Add UMA events for how the omnibox was focused on Android.

BUG=303904

Review URL: https://codereview.chromium.org/32823003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231156 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231156