Adds a method to query the nacl architecture in the hangout services extension.

BUG=

Review URL: https://codereview.chromium.org/150163004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248602 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248602