DevTools: use generic way to add "Reveal in Elements panel" to context menu

We used to add "Reveal in Elements panel" in ElementsTreeOutline. Let's instead
dispatch AppendApplicableItems with DOMNode from ElementsTreeOutine and handle
such calls in Elements panel. This would allow other panels to have DOM elements
as a target in context menu commands.

BUG=

Review URL: https://chromiumcodereview.appspot.com/22824040

git-svn-id: svn://svn.chromium.org/blink/trunk@156702 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: support screencast in remote debugging only.

Review URL: https://chromiumcodereview.appspot.com/22989009

git-svn-id: svn://svn.chromium.org/blink/trunk@156703 bbb929c8-8fbe-4397-9dbb-9b2b20218538