Migrate AppCache to simple cache backend on Android.

BUG=283896

Review URL: https://chromiumcodereview.appspot.com/23503069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224604 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224604