Rename OffscreenCanvasFrameDispatcher to CanvasResourceDispatcher

This is a step in unifying canvas and OffscreenCanvas code paths

BUG=788439

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I6f3a3f7bed8b36f502bc7ce138b4bf21920629f7
Reviewed-on: https://chromium-review.googlesource.com/1089582
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Commit-Queue: Justin Novosad <junov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#565048}
13 files changed