Continues the work to get up to TS 3.8 (latest release at time of writing).
This version of TS introduced built in definitions for web workers that include an `interface Worker` so TS gets confused when it sees us reference a `Worker`. I have renamed the imports to `PuppeteerWorker` as I couldn't figure out a way to tell TS to not load in the worker types; longer term we might consider renaming `Worker` to `PuppeteerWorker` (or an alternative) but that would be a breaking change that we don't need right now.
The other fix is similar; TypeScript doesn't differentiate between the built-in `WebSocket` type and the `ws` library. Renaming the import solves this too.
Bundled version of Puppeteer should rely on native WebSocket.
Luckily, 'ws' module supports the same interface as the native
browser websockets. This patch switches WebSocketTransport to
use the browser-compliant interface of 'ws'.
After this patch, I was able to bundle Puppeteer for browser
using the following config in `package.json`:
```json
"browser": {
"./lib/BrowserFetcher.js": false,
"ws": "./lib/BrowserWebSocket",
"fs": false,
"child_process": false,
"rimraf": false,
"readline": false
}
```
where `./lib/BrowserWebSocket` is:
```js
module.exports = WebSocket;
```
and the bundling command is:
```sh
$ browserify -r ./index.js:puppeteer > ppweb.js
```
References #2119
Currently connection assumes that transport is a websocket
and tries to handle websocket-related errors.
This patch:
- moves ConnectionTransport interface to use callbacks instead
of events. This way it could be used in browser context as well.
- introduces WebSocketTransport that implements ConnectionTransport
interface for ws.
This is a preparation step for 2 things:
- exposing `transport` option in the `puppeteer.connect` method
- better support for `browserify`
References #2119
