Add minidump_stackwalk and chrome to chromium_gpu*_builder targets

Also, get rid of the depreciated gpu_tests target.

BUG=308190
TEST=main waterfall, gpu waterfall
R=kbr@chromium.org

Review URL: https://codereview.chromium.org/26570007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229228 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229228