Depending on a flag, either applies the filter to all images,
or no images. (Later there will be an "auto" mode that tries
to heuristically filter most images but not photos and video.)

Adds support for gradients applying a color filter so that
GraphicsContext::DrawImage works correctly for gradient images,
too.

BUG=685242

Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: Iffce8257233bc81426d8ad17cbe7d6410e7f9afc
Reviewed-on: https://chromium-review.googlesource.com/533916


Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Chris harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#479954}