dither copies when decreasing precision

Still seeing the same 4444 diffs on copyTo4444 and all_bitmap_configs,
and now also 565 in all_bitmap_configs.

BUG=chromium:720105

Change-Id: I19406f57aa6d2b2f98d98c093da302b004c7cd8b
Reviewed-on: https://skia-review.googlesource.com/17419
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Matt Sarett <msarett@google.com>
1 file changed