feat: introduce puppeteer-firefox (#3628)

This adds a proof-of-concept of `puppeteer-firefox`.
This consists of two parts:
- `//experimental/juggler` - patches to apply to Firefox.
- `//experimental/puppeteer-firefox` - front-end code to
be merged with Puppeteer.

As things become more stable, we'll gradually move it out of
the experimental folder.

experimental/puppeteer-firefox/test/target.spec.js

@@ -0,0 +1,100 @@
+/**
+ * Copyright 2018 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const utils = require('./utils');
+const {waitEvent} = utils;
+const {TimeoutError} = require('../Errors');
+
+module.exports.addTests = function({testRunner, expect, product}) {
+  const {describe, xdescribe, fdescribe} = testRunner;
+  const {it, fit, xit} = testRunner;
+  const {beforeAll, beforeEach, afterAll, afterEach} = testRunner;
+
+  describe('Target', function() {
+    it('Browser.targets should return all of the targets', async({page, server, browser}) => {
+      // The pages will be the testing page and the original newtab page
+      const targets = browser.targets();
+      expect(targets.some(target => target.type() === 'page' &&
+        target.url() === 'about:blank')).toBeTruthy('Missing blank page');
+    });
+    it('Browser.pages should return all of the pages', async({page, server, browser}) => {
+      // The pages will be the testing page
+      const allPages = await browser.pages();
+      expect(allPages.length).toBe(2);
+      expect(allPages).toContain(page);
+      expect(allPages[0]).not.toBe(allPages[1]);
+    });
+    it('should be able to use the default page in the browser', async({page, server, browser}) => {
+      // The pages will be the testing page and the original newtab page
+      const allPages = await browser.pages();
+      const originalPage = allPages.find(p => p !== page);
+      expect(await originalPage.evaluate(() => ['Hello', 'world'].join(' '))).toBe('Hello world');
+      expect(await originalPage.$('body')).toBeTruthy();
+    });
+    it('should report when a new page is created and closed', async({page, server, browser}) => {
+      const [otherPage] = await Promise.all([
+        browser.waitForTarget(target => target.url() === server.EMPTY_PAGE2).then(target => target.page()),
+        page.evaluate(url => window.open(url), server.EMPTY_PAGE2),
+      ]);
+
+      expect(await otherPage.evaluate(() => ['Hello', 'world'].join(' '))).toBe('Hello world');
+      expect(await otherPage.$('body')).toBeTruthy();
+
+      let allPages = await browser.pages();
+      expect(allPages).toContain(page);
+      expect(allPages).toContain(otherPage);
+
+      const closePagePromise = new Promise(fulfill => browser.once('targetdestroyed', target => fulfill(target.page())));
+      await otherPage.close();
+      expect(await closePagePromise).toBe(otherPage);
+
+      allPages = await Promise.all(browser.targets().map(target => target.page()));
+      expect(allPages).toContain(page);
+      expect(allPages).not.toContain(otherPage);
+    });
+    it('should report when a target url changes', async({page, server, browser}) => {
+      await page.goto(server.EMPTY_PAGE);
+      let changedTarget = new Promise(fulfill => browser.once('targetchanged', target => fulfill(target)));
+      await page.goto(server.EMPTY_PAGE2);
+      expect((await changedTarget).url()).toBe(server.EMPTY_PAGE2);
+
+      changedTarget = new Promise(fulfill => browser.once('targetchanged', target => fulfill(target)));
+      await page.goto(server.EMPTY_PAGE);
+      expect((await changedTarget).url()).toBe(server.EMPTY_PAGE);
+    });
+  });
+
+  describe('Browser.waitForTarget', () => {
+    it('should wait for a target', async function({browser, server}) {
+      let resolved = false;
+      const targetPromise = browser.waitForTarget(target => target.url() === server.EMPTY_PAGE2);
+      targetPromise.then(() => resolved = true);
+      const page = await browser.newPage();
+      expect(resolved).toBe(false);
+      await page.goto(server.EMPTY_PAGE2);
+      const target = await targetPromise;
+      expect(await target.page()).toBe(page);
+      await page.close();
+    });
+    it('should timeout waiting for a non-existent target', async function({browser, server}) {
+      let error = null;
+      await browser.waitForTarget(target => target.url() === server.EMPTY_PAGE2, {
+        timeout: 1
+      }).catch(e => error = e);
+      expect(error).toBeInstanceOf(TimeoutError);
+    });
+  });
+};