Exclude one flaky test from Valgrind runs
BUG=348331
TBR=oshima

Review URL: https://codereview.chromium.org/185483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254383 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254383