feat(Page): page 'close' event (#2232)

This patch adds 'page.close' event.

References #952.

docs/api.md

@@ -39,6 +39,7 @@
   * [browser.version()](#browserversion)
   * [browser.wsEndpoint()](#browserwsendpoint)
 - [class: Page](#class-page)
+  * [event: 'close'](#event-close)
   * [event: 'console'](#event-console)
   * [event: 'dialog'](#event-dialog)
   * [event: 'domcontentloaded'](#event-domcontentloaded)
@@ -520,6 +521,10 @@ page.on('request', logRequest);
 page.removeListener('request', logRequest);
 ```
 
+#### event: 'close'
+
+Emitted when the page closes.
+
 #### event: 'console'
 - <[ConsoleMessage]>
 

lib/Page.js

@@ -103,6 +103,8 @@ class Page extends EventEmitter {
     client.on('Security.certificateError', event => this._onCertificateError(event));
     client.on('Inspector.targetCrashed', event => this._onTargetCrashed());
     client.on('Performance.metrics', event => this._emitMetrics(event));
+
+    this._target._isClosedPromise.then(() => this.emit(Page.Events.Close));
   }
 
   /**
@@ -968,6 +970,7 @@ function convertPrintParameterToInches(parameter) {
 }
 
 Page.Events = {
+  Close: 'close',
   Console: 'console',
   Dialog: 'dialog',
   DOMContentLoaded: 'domcontentloaded',

test/page.spec.js

@@ -2397,5 +2397,21 @@ module.exports.addTests = function({testRunner, expect, defaultBrowserOptions, p
         });
       });
     });
+    describe('Page.Events.Close', function() {
+      it('should work with window.close', async function({ page, browser, server }) {
+        const newPagePromise = new Promise(fulfill => browser.once('targetcreated', target => fulfill(target.page())));
+        await page.evaluate(() => window['newPage'] = window.open('about:blank'));
+        const newPage = await newPagePromise;
+        const closedPromise = new Promise(x => newPage.on('close', x));
+        await page.evaluate(() => window['newPage'].close());
+        await closedPromise;
+      });
+      it('should work with page.close', async function({ page, browser, server }) {
+        const newPage = await browser.newPage();
+        const closedPromise = new Promise(x => newPage.on('close', x));
+        await newPage.close();
+        await closedPromise;
+      });
+    });
   });
 };