Fix crash when scrolling a RenderWidget with null widget

BUG=391367

Review URL: https://codereview.chromium.org/393623002

git-svn-id: svn://svn.chromium.org/blink/trunk@178185 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: remove Node.reveal() and RemoteOject.reveal()

SDK objects should not be aware of UI-level concepts.

Review URL: https://codereview.chromium.org/391083003

git-svn-id: svn://svn.chromium.org/blink/trunk@178186 bbb929c8-8fbe-4397-9dbb-9b2b20218538