[Build Fix] Avoid multi-line comment

TBR=dmazzoni@chromium.org

Review URL: https://codereview.chromium.org/99193003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238581 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238581