Provide real GPUSupport to ash for Chrome

A recent refactor to extract src/content dependencies from ash broke
GPU feature detection for panel fitting on Chrome OS. In particular the
OutputConfigurator was set up using a stub GPUSupport object.

Fix injection of the GPUSupport object -- move its creation to the
ash::ShellDelegate interface.

BUG=chrome-os-partner:25204,chrome-os-partner:24868
TEST=existing ash_unittests

Review URL: https://codereview.chromium.org/132173006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248226 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248226