add sRGB profile and ApproximatelyEqualProfiles()

These were inevitable.

Change-Id: I87b3577a4c9a04cbbe5cfac15eca77d12225ef17
Reviewed-on: https://skia-review.googlesource.com/120423
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
11 files changed