GitLab

Create a page-set using which we can start obtaining media related 
performance metrics.

BUG=261318
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/19623003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@212212 0039d316-1c4b-4281-b951-d872f2087c98