Add an LSan suppression for an intentional leak in Blink.

BUG=121729
TBR=timurrrr@chromium.org

Review URL: https://codereview.chromium.org/63813003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233865 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233865