Fix gpu memory test.

Test was broken by https://codereview.chromium.org/183683003/ in r254108.

TBR=kbr@chromium.org,vmiura@chromium.org
BUG=348051
NOTRY=True

Review URL: https://codereview.chromium.org/184643003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254184 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254184