Roll chromium to 492629 (#230)

This patch
- rolls chromium to 492629
- migrates connection establishing to use browser target. This migration means
  that now we have a single websocket connection to browser (implemented
  in Connection class). A connection to a particular target is
  incapsulated in a new Session class.

lib/NavigatorWatcher.js

@@ -18,7 +18,7 @@ const helper = require('./helper');
 
 class NavigatorWatcher {
   /**
-   * @param {!Connection} client
+   * @param {!Session} client
    * @param {boolean} ignoreHTTPSErrors
    * @param {!Object=} options
    */