Make Canvas2DLayerBridge use CanvasResourceHost

This change makes Canvas2DLayerBridge use the instance of
CanvasResourceProvider that is stored in CanvasResourceHost.
This moves the code towards having a single location for
the resource provider for all use cases.

BUG=788439

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Ib2fbda6d2853da6ca8f35325380a1674bde0ff5d
Reviewed-on: https://chromium-review.googlesource.com/1079192
Commit-Queue: Justin Novosad <junov@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563017}
7 files changed