Moved Screenshot sync test out of telemetry and into the gpu tests

I meant to do this a little while ago, but it's become more urgent due
to bot failures on this test.

BUG=256848

Review URL: https://codereview.chromium.org/150953002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248287 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248287