Revert "Revert "fix ubsan warning""

Revert "Revert "fix ubsan warning""

This reverts commit b03d69f0709f5da09a5237922d208e587b12a06a.

Reason for revert: This is the good CL I meant to re-land.

Original change's description:
> Revert "fix ubsan warning"
>
> This reverts commit 4d1c5d676eb32ed304ee4aa410cebbc6467b59c2.
>
> Reason for revert: Valgrind requires reverting ancestor commit.
>
> Original change's description:
> > fix ubsan warning
> >
> > CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-ASAN
> >
> > Change-Id: Ic8c5d95fdb899cb5293b2bc456f61b1637ec3aed
> > Reviewed-on: https://skia-review.googlesource.com/17489
> > Reviewed-by: Mike Klein <mtklein@chromium.org>
> > Commit-Queue: Mike Klein <mtklein@chromium.org>
> >
>
> TBR=mtklein@chromium.org,herb@google.com
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-ASAN
>
> Change-Id: Idbfdc4773756aa475829c1421d10d6f341081d7b
> Reviewed-on: https://skia-review.googlesource.com/17521
> Reviewed-by: Brian Osman <brianosman@google.com>
> Commit-Queue: Brian Osman <brianosman@google.com>
>

TBR=mtklein@chromium.org,herb@google.com,reviews@skia.org,brianosman@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-Clang-GCE-CPU-AVX2-x86_64-Debug-ASAN

Change-Id: I4cf347bc578450c0cb3c91e55fdfdbe6af6fdb13
Reviewed-on: https://skia-review.googlesource.com/17526
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>