Convert drawPaint to scissor+clear when possible

Preliminary performance results: https://docs.google.com/a/google.com/spreadsheets/d/e/2PACX-1vSj_25UFcGzOPTvQgVNt3LPt5dukCgFlUc4dBpdx829mpXfss725aJH1P6CIQdyud4pkC15-tDOGNgW/pubchart?oid=1628959976&format=interactive
With a little extra fixed overhead to detect scissor+clear (visible in increased time on clear-complex), the clear-partial bench is 10X improved.
Caveat: test results only on single linux desktop.

Bug: skia:
Change-Id: I320e7be7eafdbf5c03eabbd87ab9e99421f2deba
Reviewed-on: https://skia-review.googlesource.com/c/160768
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
1 file changed