Mandoline: Support transforms and clipping of OOPIFs and events

Mandoline: Support transforms and clipping of OOPIFs and events

This CL enables basic transforms, clipping of iframe
graphical output and hit testing by leveraging
SurfaceAggregator, and SurfaceHittest.

Previously, DisplayManager's DrawViewTree was creating a
CompositorFrame with all the Surfaces in place.
SurfaceAggregator tries to put all the Surfaces together
but finds it has no work to do because all the
SurfaceDrawQuads are already in one CompositorFrame. By not
including subtrees of Views with Surfaces in the
CompositorFrame DisplayManager generates, we left
SurfaceAggregator do the heavy lifting for
transforms/clipping/opacity/etc.

BUG=496953
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1328953003

Cr-Commit-Position: refs/heads/master@{#349547}