There seem about a zillion possible ways to slice this.
This adds and uses SkMallocPixelRef::ZeroedPRFactory.
I'm not married to it.
This appears to clear up a hot spot in the benchmark referenced in this bug:
BUG=516426
I'm not confident enough on Windows to declare that definitively yet.
It probably helps all other non-opaque layers too. Possibly significantly.
So I don't forget, I profiled this:
out/Release/performance_browser_tests.exe --gtest_filter=TabCapturePerformanceTest.Performance/2 --single-process
No diffs:
https://gold.skia.org/search2?issue=1430593007&unt=true&query=source_type%3Dgm&master=falseTBR=reed@google.com
Review URL: https://codereview.chromium.org/1430593007
cd49541524