Introduced AndroidDeviceProvider to simplify testing.

TBR=pfeldman
BUG=308514

Review URL: https://codereview.chromium.org/26568004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230374 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230374