This CL is a first pass at implementing container in fn2. In this approach,
Container is a Component that builds a number of RenderNodeWrappers depending
on what is needed.
R=ianh@google.com
Review URL: https://codereview.chromium.org/1158983005
Prevously we listened for events on the document and then walked up the
component hierarchy looking for EventListenerNodes. Now we do something similar
by hooking the event dispatching logic in the AppView.
R=eseidel@chromium.org
Review URL: https://codereview.chromium.org/1153343004
