Fix/simplify equal_pixels

Luckily without maxDiff, we can completely remove the buggy
implementation of diff().

Bug: skia:
Change-Id: I365fb6e595e3b670950a016bcb8ee553d85a8b75
Reviewed-on: https://skia-review.googlesource.com/155844
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
4 files changed