Revert "Make SkBitmap/SkPixmap::erase* do so in sRGB"

This reverts commit 6f44647e529924e414ee05462b1ef7b7d1cfb767.

Reason for revert: checking to see if this is blocking the Chrome roll

Original change's description:
> Make SkBitmap/SkPixmap::erase* do so in sRGB
> 
> We generally consider untagged colors to be sRGB, so this makes us more
> consistent with other parts of the API.
> 
> Add a test.
> 
> Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
> Change-Id: I5468c86ad92164797a65ffd9fbe471e01a97a2ca
> Reviewed-on: https://skia-review.googlesource.com/c/179245
> Commit-Queue: Leon Scroggins <scroggo@google.com>
> Reviewed-by: Mike Reed <reed@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>
> Reviewed-by: Brian Osman <brianosman@google.com>

TBR=djsollen@google.com,mtklein@google.com,scroggo@google.com,brianosman@google.com,reed@google.com

Change-Id: Ia592adf2c790d294da1e32c1e83f9f34e81d79cc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Reviewed-on: https://skia-review.googlesource.com/c/182083
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
4 files changed