Report GPU memory usage to DevTools

Extract GPU memory usage statistics and pass it to DevTools.

BUG=326497

Review URL: https://codereview.chromium.org/110883005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240084 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240084