Updating build-webapp script to append the client id extension for app remoting apps automatically.

BUG=

Review URL: https://codereview.chromium.org/1070903002

Cr-Commit-Position: refs/heads/master@{#324322}

remoting/webapp/build-webapp.py

@@ -355,7 +355,7 @@ def buildWebApp(buildtype, version, destination, zip_path,
     if not app_client_id:
       raise Exception('Invalid app_client_id passed in: "' +
           app_client_id + '"')
-    apiClientIdV2 = app_client_id
+    apiClientIdV2 = app_client_id + '.apps.googleusercontent.com'
   else:
     apiClientIdV2 = google_api_keys.GetClientID('REMOTING_IDENTITY_API')