Android: Guard off desktop notifications

We currently have no system in place to perform desktop
notifications on Android.  This CL guards off certain bits
of code and prevents the files in browser/notifications/*
from being compiled when notifications are disabled.

BUG=http://crbug.com/115320
TEST=


Review URL: http://codereview.chromium.org/9447034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@124305 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/build/common.gypi b/build/common.gypi
index f5bc3a5..487ff93 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -747,6 +747,9 @@
         'configuration_policy%': 0,
         'input_speech%': 0,
         'java_bridge%': 1,
+
+        # Set to 1 once we have a notification system for Android.
+        # http://crbug.com/115320
         'notifications%': 0,
 
         # Builds the gtest targets as a shared_library.