This patch:
- adds `worker.evaluate` and `worker.evaluateHandle` methods as a shortcut to their execution context equivalents.
- makes the error messages a bit nicer when interacting with a closed worker (as opposed to a closed page).
- moves the worker tests into their own spec file.
This patch drops the markdown-toc module and instead rolls out
our own simple markdown table-of-contents generator.
As a side effect, it fixes links to `page.$` and `page.$$`.
Docs about `page.$$eval` and `frame.$$eval` are not accurate and might be confusing. `document.querySelectorAll` returns `NodeList`, while `frame.$$eval` is actually doing `Array.from(querySelectorAll(selector))`, which actually returns an array.
This makes things this possible:
`await page.$$eval('div', divs => divs.map...)`
This patch fixes docs to mention that $$eval is actually performing:
`Array.from(querySelectorAll(selector))`
Which will let the user understand that the element he receives is an array, and not a NodeList.
This adds `page.workers()`, and two events `workercreated` and `workerdestroyed`. It also forwards logs from a worker into the page `console` event.
Only dedicated workers are supported for now, ServiceWorkers will probably work differently because they aren't necessarily associated with a single page.
Fixes#2350.
This patch introduces Browser Contexts and methods to manage them:
- `browser.createIncognitoBrowserContext()` - to create new incognito
context
- `browser.browserContext()` - to get all existing contexts
- `browserContext.dispose()` - to dispose incognito context.
Fixes#85.
Today, `page.close()` method doesn't run page's beforeunload listeners.
This way users can be sure that `page.close()` actually closes the
page.
This patch adds an optional `runBeforeUnload` option to the
`page.close()` method that would run beforeunload listeners. Note:
running beforeunload handlers might cancel page closing.
Fixes#2386.
Last release v1.3.0 had an error in the documentation, claiming
it wasn't released.
This patch makes sure we have a little bit of automation in place
to save us from this in future.
This patch introduces a new `pipe` option to the launcher to connect over a pipe.
In certain environments, exposing web socket for remote debugging is a security risk.
Pipe connection eliminates this risk.
This patch adds support for `timeout: 0` to disable timeout for the following functions:
- `page.waitForFunction`
- `page.waitForXPath`
- `page.waitForSelector`
and their `frame` counterparts.
Fixes#2200
This patch:
- starts fulfilling security details for redirect responses
- changes `response.securityDetails()` to return null if the response
is served over non-secure connection
This patch introduces ExecutionContext.frame() that returns Frame
associated with this Execution Context.
This allows to associate console messages with the originating frame,
if any.
This patch:
- introduces `SecurityDetails` class that exposes a set of fields that describe properties of secure connection
- introduces method `response.securityDetails()` that returns an instance of `SecurityDetails` object.
This patch introduces `BrowserFetcher` class that manages
downloaded versions of products.
This patch:
- shapes Downloader API to be minimal yet usable for our needs. This
includes removing such methods as `Downloader.supportedPlatforms` and
`Downloader.defaultRevision`.
- makes most of the fs-related methods in Downloader async. The only
exception is the `Downloader.revisionInfo`: it has stay sync due to the
`pptr.executablePath()` method being sync.
- updates `install.js` and `utils/check_availability.js` to use new API
- finally, renames `Downloader` into `BrowserFetcher`
Fixes#1748.
This patch:
- introduces `test/assets/cached` folder and teaches server to cache
all the assets from the folder
- introduces `test/assets/serviceworkers` folder that stores all the
service workers and makes them register with unique URL prefix
- introduces `Response.fromCache()` and `Response.fromServiceWorker()`
methods
Fixes#1551.
This patch:
- migrates CI to use NPM
- drops lockfiles (`yarn.lock`). Lockfiles are ignored by package
managers when the package is installed as a dependency, so this makes CI closer to the
installation our clients run.
This patch introduces a `slowMo` option to the `puppeteer.connect` method. The option
is similar to the one in `puppeteer.launch` and is used to slow down the connection.
This patch:
- introduces `page.waitForXPath` method
- introduces `frame.waitForXPath` method
- amends `page.waitFor` to treat strings that start with `//` as xpath queries.
Fixes#1757.
feat: expose raw devtools protocol connection
This patch introduces `target.createCDPSession` method that
allows directly communicating with the target over the
Chrome DevTools Protocol.
Fixes#31.
This patch:
- teaches page.waitFor* methods to accept JSHandles
- starts returning JSHandles from page.waitFor* calls.
BREAKING CHANGE: this patch starts allocating `JSHandle`/`ElementHandle` instances for every call to `page.waitFor*` functions. These handles should be disposed manually to avoid memory consumption.
Fixes#1703, fixes#1654, fixes#1724.
This patch adds two new methods to the `page.coverage` namespace:
- `page.coverage.startCSSCoverage()` - to initiate css coverage
- `page.coverage.stopCSSCoverage()` - to stop css coverage
The coverage format is consistent with the JavaScript coverage.
This patch introduces a new `page.coverage` namespace with two methods:
- `page.coverage.startJSCoverage` to initiate JavaScript coverage
recording
- `page.coverage.stopJSCoverage` to stop JavaScript coverage and get
results
This patch:
- adds `puppeteer.defaultArgs()` method to get default arguments that are used to launch chrome
- adds `ignoreDefaultArgs` option to `puppeteer.launch` to avoid using default puppeteer arguments
Fixes#872
The patch converts all the getters in the codebase into the methods.
For example, the `request.url` getter becomes the `request.url()`
method.
This is done in order to unify the API and make it more predictable.
The general rule for all further changes would be:
- there are no getters/fields exposed in the api
- the only exceptions are "namespaces", e.g. `page.keyboard`
Fixes#280.
BREAKING CHANGE:
This patch ditches getters and replaces them with methods throughout
the API. The following methods were added instead of the fields:
- dialog.type()
- consoleMessage.args()
- consoleMessage.text()
- consoleMessage.type()
- request.headers()
- request.method()
- request.postData()
- request.resourceType()
- request.url()
- response.headers()
- response.ok()
- response.status()
- response.url()
This refactors the page.content and page.setContent methods to be defined on the Frame class. This allows access from the Page still but also on all frames.
Fixes#754
In Blink, frames don't necesserily have execution context all the time.
DevTools Protocol precisely reports this situation, which results in
Puppeteer's frame.executionContext() being null occasionally.
However, from puppeteer point of view every frame will have at least a
default executions context, sooner or later:
- frame's execution context might be created naturally to run frame's
javascript
- if frame has no javascript, devtools protocol will issue execution
context creation
This patch builds up on this assumption and makes frame.executionContext()
to be a promise.
As a result, all the evaluations await for the execution context to be created first.
Fixes#827, #1325
BREAKING CHANGE: this patch changes frame.executionContext() method to return a promise.
To migrate onto a new behavior, await the context first before using it.
The SIGHUP signal is sent whenever the controlling terminal is closed.
On Windows, SIGHUP is emulated by libuv, and will be the only signal we
receive before the application will be terminated.
This patch starts handling SIGHUP in the same way we handle SIGTERM.
Fixes#1367.
SIGTERM signal is widely used to notify application that it will be shut down.
This patch starts listening to SIGTERM event to gracefully retire
chromium instance.
References #1047.
This patch adds `Frame.select` method that does the same functionality as
former `Page.select`, but on a per-frame level.
The `Page.select` method becomes a shortcut for the ÷main frame's select.
Fixes#1139
This patch migrates puppeteer to support PlzNavigate chromium
project.
As a consequence of this patch, we no longer wait for both
requestWillBeSent and requestIntercepted events to happen. This should
resolve a ton of request interception bugs that "hanged" the loading.
Fixes#877.
This adds more examples for using `keyboard.type` and `keyboard.press`. It adds warnings about Shift affecting or not affecting the text generated by certain methods.
fixes#723
The jontewks buildpack worked great for running Chrome headless, but it did not include support for Chinese characters and the PDF rendering I was attempting was not usable. This fix brings in a few custom fonts to allow PDF generation to utilize the fonts.
The idea came from https://github.com/dscout/wkhtmltopdf-buildpack/pull/14/files
This roll includes:
- crrev.com/510651 that changes request interception methods in protocol
- s/Page.setRequestInterceptionEnabled/Page.setRequestInterception
BREAKING CHANGE
Page.setRequestInterceptionEnabled is renamed into
Page.setRequestInterception.
This patch adds "options" parameter to the `page.setContent` method. The
parameter is the same as a navigation parameter and allows to specify
maximum timeout to wait for resources to be loaded, as well as to
describe events that should be emitted before the setContent operation
would be considered successful.
Fixes#728.
This patch adds support to multiple events that could be passed inside
navigation methods:
- Page.goto
- Page.waitForNavigation
- Page.goForward
- Page.goBack
- Page.reload
Fixes#805
This patch adds a new `domcontentloaded` option to a bunch of navigation
methods:
- Page.goto
- Page.waitForNavigation
- Page.goBack
- Page.goForward
- Page.reload
Fixes#946.
This patch:
- migrates navigation watcher to use protocol-issued lifecycle events.
- removes `networkIdleTimeout` and `networkIdleInflight` options for
`page.goto` method
- adds a new `networkidle0` value to the waitUntil option of navigation
methods
References #728.
BREAKING CHANGE:
As an implication of this new approach, the `networkIdleTimeout` and
`networkIdleInflight` options are no longer supported. Interested
clients should implement the behavior themselves using the `request` and
`response` events.
BREAKING CHANGE:
This patch lets key names be code in addition to key. When specifying a code, the proper text is generated assuming a standard US keyboard layout. e.g Digit5 -> "5" or "%" depending on Shift.
* location is now specified. #777
* Using unknown key names now throws an error. #723
* Typing newlines now correctly presses enter. #681
feat(interception): Implement request.respond method
This patch implements a new Request.respond method. This
allows users to fulfill the intercepted request with a hand-crafted
response if they wish so.
References #1020.
Currently, JSHandle.jsonValue() is implemented as in-page JSON.stringify
call and consequent JSON.parse in node. This approach proved to be
unfortunate for automation purposes: if page author overrode the
Object.prototype.toJSON method, then it's harder for puppeteer to
interact with the page.
This patch switches JSHandle.jsonValue to use protocol serialization
that ignores toJSON property. THis also changes the `page.evaluate`
behavior since it is based on JSHandle.jsonValue().
Fixes#1003.
BREAKING CHANGE:
`page.evaluate` no longer calls toJSON when generating return value.
For the old behavior, do JSON.parse/JSON.stringify manually:
```js
const json = JSON.parse(await page.evaluate(() => JSON.stringify(obj)));
```
This patch:
- introduces Target class that represents any inspectable target, such as service worker or page
- emits events when targets come and go
- introduces target.page() to instantiate a page from a target
Fixes#386, fixes#443.
Similarly to the `request.response()` method, this patch adds
`request.failure()` method that returns error details for the failed
requests.
Fixes#901.
This patch:
- changes `browser.close` to terminate browser.
- introduces new `browser.disconnect` to disconnect from a browser without closing it
This patch: fixes#918, fixes#989
BREAKING CHANGE:
`browser.close()` will always close a browser, even if it was initialized with
`puppeteer.connect`. To disconnect from a remote browser, use `browser.disconnect()` instead.
This patch starts generating input events for `keyboard.down`, addressing bullet 2 of
#723. With this patch, there's no longer any difference between `keboard.press('a')` and
`keyboard.press('a', {text: 'a'})`.
BREAKING CHANGE:
`keyboard.down('a')` starts generating input event (wasn't the case before).
References #723
This patch:
- deprecates injectFile as it was confused with the addScriptTag
- accepts an options object in addScriptTag which supports properties url, path and content.
- accepts an options object in addStyleTag which supports properties url, path and content.
Fixes#949.
BREAKING CHANGE:
- the addStyleTag/addScriptTag have changed;
- the injectFile was removed in favor of (addStyleTag({path:}).
This patch introduces `Page.queryObjects` and
`ExecutionContext.queryObjects` methods to query JavaScript heap
for objects with a certain prototype.
Fixes#304.
The page.plainText is confusing: it's unclear what kind of text it
returns, textContent or innerText. It's also easily polyfillable and
doesn't seem to be used.
BREAKING CHANGE: the page.plainText is not existing any more.
Instead, use `page.evaluate(() => document.body.innerText)`.
This patch:
- updates JSHandle.toString to make a nicer description for primitives
- excludes JSHandle.toString from documentation to avoid its abuse
References #382
This patch moves resourceType to be all small-caps. This aligns
with our convention that all string constants should be smallcaps.
BREAKING CHANGE: this patch changes the constants of the
request.resourceType to be all small-caps.
This patch:
- adds `ElementHandle.boundingBox()` method to get bounding box of element relative
to the page
- adds `ElementHandle.screenshot()` method to capture a screenshot of an element
This patch:
- adds input methods to ElementHandle, such as ElementHandle.type and ElementHandle.press
- changes `page.type` to accept selector as the first argument
- removes `page.press` method. The `page.press` is rarely used and doesn't operate with selectors; if there's a need to press a button, `page.keyboard.press` should be used.
BREAKING CHANGE: `page.type` is changed, `page.press` is removed.
Fixes#241.
This patch:
- introduces ExecutionContext class that incapsulates javascript
execution context. An examples of execution contexts are workers and
frames
- introduces JSHandle that holds a references to the javascript
object in ExecutionContext
- inherits ElementHandle from JSHandle
Fixes#382.
This patch allows passing 0 to disable timeout for the following methods:
- page.goto
- page.waitForNavigation
- page.goForward
- page.goBack
Fixes#782.
This patch introduces ConsoleMessage type and starts dispatching
it for the 'console' event.
BREAKING CHANGE: this breaks the api of the 'console' event.
Fixes#744.
This patch adds support for PUPPETEER_SKIP_CHROMIUM_DOWNLOAD
variable in npm config.
This aligns the variable with the rest of supported environment variables.
This lets the user pass `...args` into `page.waitFor`. It also clarifies that the docs that `options` is not optional if `...args` are specified.
Fixes#770
Since protocol ignores all HTTP headers that don't have string
value, this patch starts validating header key-values before
sending them over the protocol.
Fixes#713.
This patch:
- makes `browser.close()` return a promise that resolves when browser gets closed
- starts closing chrome gracefully if a custom `userDataDir` is supplied
Fixes#527
This patch:
- teaches `page.evaluate` to accept ElementHandles as parameters
- removes `ElementHandle.evaluate` method since it's not needed any
more
References #382
It's very bad to have 'unhandled promise rejection' that can't be
handled in user code. These errors will exit node process in a near
future.
This patch avoids 'unhandled promise rejection' while sending protocol
messages.
This patch:
- introduces `puppeteer:error` debug scope and starts using it for all
swalloed errors.
- makes sure that every `client.send` method is either awaited or its
errors are handled.
- starts return promises from Request.continue() and Request.abort().
- starts swallow errors from Request.contine() and Request.abort().
The last is the most important part of the patch. Since
`Request.continue()` might try to continue canceled request, we should
disregard the error.
Fixes#627.
This patch:
- adds `page.touchscreen` namespace, similar to `page.mouse` and `page.keyboard`.
- adds tapping to multiple layers:
- `page.touchscreen.tap`
- `page.tap` - convenience method which accepts selector
- `elementHandle.tap`
Fixes#568 and #569.
This patch:
- starts skipping chromium download if `PUPPETEER_SKIP_CHROMIUM_DOWNLOAD` env variable is set
- adds description of support env variables to the `docs/api.md`.
References #603
This patch:
- switches to objects instead of maps for headers (in Request, Response and
page.setExtraHTTPHeaders)
- converts all header names to lower case
Fixes#547, fixes#509
This patch bumps version to 0.9.1-alpha.
This should emphasize that the documentation is related to the tip-of-tree
version of puppeteer, not to the latest release.
This patch:
- adds a 'timeout' launcher option that constrains the time for chromium to launch.
- adds a 'handleSIGINT' launcher option that is `true` by default and that closes chrome instance
Fixes#363.
* Replace let with const in examples when appropriate.
* Unify spacing.
* Fix possible copy-paste artifacts.
* Eliminate one unhandled promise rejection ('Target closed').
This patch:
- removes the `page.uploadFile` method
- adds `elementHandle.uploadFile` method.
Motivation: `elementHandle.uploadFile` is rarely used, so it doesn't worth it
to keep it on page.
This patch:
- refactors Connection to use a single remote debugging URL instead of a
pair of port and browserTargetId
- introduces Puppeteer.connect() method to attach to already running
browser instance.
Fixes#238.
This patch starts emitting 'error' event when page crashes.
'error' events have special treatment in node, so page crashes
become observable for users.
Fixes#262.
This patch:
- split browser launching logic from Browser into `lib/Launcher.js`
- introduce `puppeteer` namespace which currently has a single `launch`
method to start a browser
With this patch, the browser is no longer created with the `new
Browser(..)` command. Instead, it should be "launched" via the
`puppeteer.launch` method:
```js
const puppeteer = require('puppeteer');
puppeteer.launch().then(async browser => {
...
});
```
With this approach browser instance lifetime matches the lifetime of
actual browser process. This helps us:
- remove proxy streams, e.g. browser.stderr and browser.stdout
- cleanup browser class and make it possible to connect to remote
browser
- introduce events on the browser instance, e.g. 'page' event. In case
of lazy-launching browser, we should've launch browser when an event
listener is added, which is unneded comlpexity.
This patch:
- changes interception API so that it better aligns with what we'd like to see
in #121
- fixes the issue with redirect interception
Fixes#217.
These commands proved to be over-complicating the documentation source.
We should keep documentation source as simple to edit as possible to
make it friendly to contributions.
This patch keeps the gen:version command as it is non-invasive.
This patch implements 'autoRepeat' functionality for `keyboard.down`.
With this patch, the subsequent calls to `keyboard.down` would generate
an event with 'autoRepeat` flag set to true.
Closes#157
The motivation behind the patch:
- examples are probably the most valuable thing in the doc
- currently, one would need to navigate to `page.evaluate` and then
click to the `frame.evaluate` to see the example.
- with this patch, all the descriptions for the shortcut methods are
copied as well. So there's an example for `page.evaluate` right
away.
Drive-by: fix links for `page.$` and `page.$$`
The two tasks allow to copy text from one part of document to another.
This comes handy in organizing the documentation for our shortcut
methods, which should be exactly the same as the original methods.
The tasks work like this:
- the gen:copy(id) task saves a part of document under the name 'ID'.
- the gen:paste(id) task pastes text saved with id 'ID'
This patch also fixes a bunch of links in documentation, as well as
migrating `api.md` to use the two tasks.
This patch implements simple markdown preprocessor. The goal
is to generate certain parts of markdown, such as:
- puppeteer version
- chromium revision
- table-of-contents
- copy/paste parts of documentation (for shortcut methods)
This patch:
- teaches page.uploadFile() to resolve given file paths against
current working directory. This aligns paths handling with all the
other methods
- moves page.uploadFile() under Frame
- changes test to use relative path for file upload
The Body class was inlined in the Request and Response classes.
This patch:
- removes the Body class
- adds Request.postData public property
- adds Response.buffer(), Response.text() and Response.json() methods
Fixes#106.
The page.waitForFunction method allows to wait for a general predicate.
The predicate will be continiously polled for in page, until
it either returns true or the timeout happens.
The polling parameter could be one of the following:
- 'raf' - to poll on every animation frame
- 'mutation' - to poll on every dom mutation
- <number> - to poll every X milliseconds
References #91
This patch:
- removes Body.arrayBuffer. This method is redundant since there's
already a Body.buffer() method
- removes Body.bodyUsed getter.
References #106
This patch:
- renames page.setHTTPHeaders into page.setExtraHTTPHeaders
- starts using Map instead of Object to align with other headers
arguments
Fixes#112.
This patch improves on page.evaluate to accept a string.
The string can have a trailing '//# sourceURL=' comment which would
name the evaluation to make stacks beautiful.
In order to make sourceURL comments possible, this patch:
- removes wrapping of the client function into `Promise.resolve()`
- stops passing `awaitPromise` parameter to `Runtime.evaluate`
- starts to await promise via the `Runtime.awaitPromise` if the return type of the evaluation
is promise
closes#118
This patch removes Header class and substitutes it with a simple
Map object.
The map is chosen over the vanilla object since it has explicit
order of headers which we'd like to preserve.
References #106.
This patch renames page.evaluateOnInitialized into
page.evaluateOnNewDocument to better align with the protocol and with
what the method is actually doing.
Fixes#119.
This patch removes the InterceptedRequest.isHandled method. There's
always a single request interceptor who owns all the intercepted
requests and who know if they were handled.
References #115.
This patch:
- adds Mouse class which holds mouse state and implements mouse primitives,
such as moving, button down and button up.
- implements high-level mouse api, such as `page.click` and `page.hover`.
References #40, References #89
This patch:
- introduces page.waitForSelector to wait for the selector to appear
- introduces polymorphic page.waitFor method, which accepts
either string (and in this case is a shortcut for page.waitForSelector)
or number (and in this case it's a promisified timeout).
References #91.
This patch implements timeout option for page.waitFor. The function
will throw if the selector doesn't appear during timeout milliseconds
of waittime.
References #89, #91.
This patch adds a 'visible' option to the Page.waitFor method, making
it possible to wait for the element to become actually visible.
References #89, #91.
This patch:
- gets rid of `page.emulate` and `page.emulatedDevices`
methods. Instead, it is suggested to use `page.setViewport()`
and `page.setUserAgent()` methods.
- moves DeviceDescriptors to the top level of the puppeteer so that
it is convenient to require them.
- improves on documentation to describe the suggested emulation
approach.
References #88.
This patch converts lib/DevicesDescriptors from a devtools front-end
format into a puppeteer format.
This patch does this via introducing a scripts utils/fetch_devices.js
which grabs devices from upstream of DevTools Front-end and
converts them into puppeteer devices.
References #88.
This patch introduces Page.waitForNavigation which allows to wait
for render-initiated navigation.
This patch also does a nice refactoring, replacing Navigator with NavigatorWatcher which
is not a part of a page state.
References #89
This patch:
- renames Page.printToPDF into page.pdf
- adds a 'path' option to the page.pdf options instead of a separate
`filePath` parameter
- improves on the documentation for the `page.pdf`
References #39.
This patch:
- adds event linting to the doclint
- improves `api.md` to add events and more information about
classes reported by events.
References #14.
This patch unifies Documentation.Method with Documentation.Property,
making it possible to verify sorting order across methods and
properties.
References #14.
This patch:
- fixes a typo in documentation linter, which resulted in only
certain method arguments being linted.
- adds missing arguments to the documentation
References #14.
This patch introduces a general Documentation.diff method, which
produces a diff of two documentations.
With this, the patch teaches documentation linter to lint method arguments.
References #14.
This patch remove remoteDebuggingPort option. Instead, browser
is launched with '--remote-debugging-port=0' flag, letting browser
to pick any port. The puppeteer reads the port number from the
browser's stderr stream.
This change cuts average browser start time from 300ms to 250ms
on my machine. This happens since puppeteer doesn't have to probe
network once every 100ms, waiting for the remote debugging server to
instantiate.
Fixes#21.
This patch changes Page.navigate API:
- Page.navigate now resolves to the main page response
- Page.navigate throws errors if there's no main page response,
e.g. in case of SSL errors, max navigation timeout,
or invalid url.
This patch also adds httpsServer with a self-signed certificates
for the testing purposes.
Fixes#10.
This patch implements documentation linter, which leaves under `test/doclint`
folder.
The documentation linter works like this:
1. Parse javascript source code with esprima and construct a "documentation" out of source code
2. Generate HTML out of `api.md` and traverse the HTML with puppeteer.
3. Make sure javascript aligns nicely with HTML
The documentation linter adds the following commands:
- `yarn doc` - to test that documentation covers all the relevant apis
- `yarn generate-toc` - to update the table-of-contents for the `api.md`
This patch implements NetworkManager, which encapsulates all the
interaction with Network domain.
The NetworkManager also uses partial implementation of Request and
Response classes, defined in the Fetch API specification.
References #26
This patch improves on api.md so that the raw md is human-readable
and the rendering is still good.
The next step would be linting markdown so that it's up-to-date and neat.
References #14.
This patch refactors Page.screenshot api, accoring to the discussion
in #5:
- Page.screenshot accepts single optional options object
- Page.saveScreenshot is removed
- Page.screenshot assumes 'png' screenshot if no type is set and no
'path' property is given
Fixes#5.
This patch makes Page.evaluate await promise if one is
returned by the evaluated code.
This makes the Page.evaluateAsync unneeded, so the patch
removes it.
Fixes#11.
This patch removes the Page.setBlockedURLs method. The
functionality is trivially implementable with the request
interception (see examples/loadurlwithoutcss.js).
Fixes#1.
It turns page.size() and page.setSize() methods are slightly
confusing since there multiple different sizes (layout size,
content size, viewport size..)
This patch renames Page.{size,setSize} methods into
Page.{viewportSize,setViewportSize} methods to avoid confusion.
This patch adds docs/api.md file which contains API description
for the puppeteer API. This patch adds the API outline, which
doesn't not have explanations and samples.
