Alternative workaround for mac kernel bug.

BUG=298276

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=227999

Review URL: https://codereview.chromium.org/25325002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228569 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228569