Exclude Media Galleries strings for Android.

Android does not use Media Galleries.

BUG=326023

Review URL: https://codereview.chromium.org/160073004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250702 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250702