Support browser contexts to launch different sessions

Support browser contexts (Target.createBrowserContext) so to avoid launching multiple instances if one wants a pristine session. See proposal https://github.com/GoogleChrome/puppeteer/issues/66 and original discussion at https://github.com/cyrus-and/chrome-remote-interface/issues/118.

A viable user scenario might be testing several users logged in simultaneously into the service. We might expose browser contexts as a string literal option to the browser.newPage:

browser.newPage(); // creates a new page in a default browser context
browser.newPage({ context: 'default' }); // same as previous call
browser.newPage({ context: 'another-context' }); // creates a page in another browser context

[barbolo]

Ok, I got this working. Thanks for the tip, @ks07 .

const puppeteer = require('puppeteer');
const Page = require('puppeteer/lib/Page');

async function newPageWithNewContext(browser) {
  const {browserContextId} = await browser._connection.send('Target.createBrowserContext');
  const {targetId} = await browser._connection.send('Target.createTarget', {url: 'about:blank', browserContextId});
  const client = await browser._connection.createSession(targetId);
  const page = await Page.create(client, browser._ignoreHTTPSErrors, browser._screenshotTaskQueue);
  page.browserContextId = browserContextId;
  return page;
}

async function closePage(browser, page) {
  if (page.browserContextId != undefined) {
    await browser._connection.send('Target.disposeBrowserContext', {browserContextId: page.browserContextId});
  }
  await page.close();
}

(async () => {
  const browser = await puppeteer.launch();
  const page = await newPageWithNewContext(browser);
  await page.goto('https://example.com');
  console.log(await page.cookies());

  await closePage(browser, page);
  await browser.close();
})();

UPDATE (2017-11-04): I’ve updated the example with a suggestion on how to close the page and its context.

[SirNeural]

Any updates to this issue now that pptr has hit v1.0.0? Supporting page contexts for isolations of sessions without having to make separate browser instances seems like a feature that I’d really like to see implemented!