Revert of add asserts around results from requestLock (patchset #3 id:40001 of https://codereview.chromium.org/1155403003/)

Reason for revert:
asserts in ui/gfx unittests (need to investigate why)

[ RUN      ] RenderTextTest.SelectionKeepsLigatures
[14602:14602:0529/134016:16779526944:INFO:SkPixelRef.cpp(164)] ../../third_party/skia/src/core/SkPixelRef.cpp:164: failed assertion "pixels"

Original issue's description:
> add asserts around results from requestLock and lockPixels, ensuring that true always means we have non-null pixels (and non-null colortable if that matches the colortype)
>
> BUG= 491975
> TBR=
>
> Committed: https://skia.googlesource.com/skia/+/f941a68126d8fe647eaea902c244c466568b7809

TBR=scroggo@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG= 491975

Review URL: https://codereview.chromium.org/1159013006
2 files changed