Remove LayerScrollOffsetDelegate, make all input paths go thru proxy.
This removes the cc::LayerScrollOffsetDelegate interface, moving it
into the InputHandlerClient interface.
It also removes the pointer to cc::LayerTreeHostImpl (as a
cc::InputHandler*) from the WebView embedder code. Instead make the
WebView code always go through the SynchronousInputHandlerProxy (which
is the InputHandlerProxy) to talk to the compositor about input-related
things.
R=boliu, jdduke@chromium.org
BUG=531746
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
Review URL: https://codereview.chromium.org/
1353013002
Cr-Commit-Position: refs/heads/master@{#350056}