Hangouts Remote Desktop Part V - It2MeHelpeeChannel

This CL introduces the class, which relays messages between the Hangouts web page (Hangouts)
and the It2Me Native Messaging Host (It2MeHost) for the helpee (The hangout
participant who is receiving remoting assistance).

It runs in the background page. It contains a chrome.runtime.Port object,
representing a connection to Hangouts and a remoting.It2MeHostFacade object,
representing a connection to the IT2Me Native Messaging Host.

After this CL, the webapp is ready for integration with Hangouts, with the exception of 
two outstanding work items below that must be addressed before launching:
1. Fetch the OAuthToken using remoting.OAuth2 for the v1 app (crbug.com/405130).
2. Show the confirm dialog using chrome.app.AppWindow for the v2 app (crbug.com/405139).

Review URL: https://codereview.chromium.org/484353002

Cr-Commit-Position: refs/heads/master@{#291011}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@291011 0039d316-1c4b-4281-b951-d872f2087c98

remoting/remoting_webapp_files.gypi

@@ -151,6 +151,7 @@
       'webapp/unittests/base_unittest.js',
       'webapp/unittests/l10n_unittest.js',
       'webapp/unittests/menu_button_unittest.js',
+      'webapp/unittests/it2me_helpee_channel_unittest.js',
       'webapp/unittests/it2me_helper_channel_unittest.js',
       'webapp/unittests/it2me_service_unittest.js'
     ],
@@ -181,13 +182,19 @@
       # '<@(remoting_webapp_js_browser_test_files)'
     ],
 
-    # The JavaScript files that are used as background pages.
+    # The JavaScript files that are used in the background page.
     'remoting_webapp_background_js_files': [
       'webapp/base.js',
       'webapp/client_session.js',
+      'webapp/error.js',
+      'webapp/host_installer.js',
+      'webapp/host_session.js',
+      'webapp/it2me_host_facade.js',
+      'webapp/plugin_settings.js',
       'webapp/typecheck.js',
       'webapp/background/app_launcher.js',
       'webapp/background/background.js',
+      'webapp/background/it2me_helpee_channel.js',
       'webapp/background/it2me_helper_channel.js',
       'webapp/background/it2me_service.js',
     ],

remoting/webapp/background/background.js

@@ -53,6 +53,8 @@ function initializeBackgroundService(appLauncher) {
     remoting.it2meService = null;
   });
 
+  remoting.settings = new remoting.Settings();
+
   chrome.runtime.onSuspendCanceled.addListener(initializeIt2MeService);
   initializeIt2MeService();
 }