Fully unreference run_gpu_test and delete it.

Second try. TBR'ing because the CQ won't catch failures in this area
anyway; I'll watch the bots as this lands.

BUG=346585
TBR=zmo@chromium.org,skyostil@chromium.org,yfriedman@chromium.org

Review URL: https://codereview.chromium.org/177653008

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253070 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253070