GitLab

This removes the need for ClientSession to implement ClipboardStub
and proxy clipboard events itself.

BUG=118511


Review URL: https://chromiumcodereview.appspot.com/10831223

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@152281 0039d316-1c4b-4281-b951-d872f2087c98