Send coverage VA as floats instead of bytes
NOTREECHECKS=True

BUG=skia:

Review URL: https://codereview.chromium.org/700943005
Detect loops overflow for gpu benches.

NOTREECHECKS=true

BUG=skia:

Review URL: https://codereview.chromium.org/709473002
Revert of Revert of Turn on NVPR 4x MSAA by default when supported in DM and nanobench. (patchset #1 id:1 of https://codereview.chromium.org/693933004/)

Reason for revert:
Try again with loops overflow fix landed.

Original issue's description:
> Revert of Turn on NVPR 4x MSAA by default when supported in DM and nanobench. (patchset #2 id:20001 of https://codereview.chromium.org/704563003/)
>
> Reason for revert:
> Timing out on nvpr when drawing conics. Fix will take some thought so reverting for now.
>
> Original issue's description:
> > Turn on NVPR 4x MSAA by default when supported in DM and nanobench.
> >
> > This brings DM and nanobench's default configs in line with GM's.
> >
> > BUG=skia:
> >
> > Committed: https://skia.googlesource.com/skia/+/31f88675718966bbb7f09718b40de10c7e214739
>
> TBR=bsalomon@google.com,mtklein@google.com,mtklein@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/d5cd4ee5b81b51e43be7ed13f3c0f0f6c1b3fe14

TBR=bsalomon@google.com,mtklein@chromium.org,egdaniel@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/685923003