[OT-PW] Implement RasterWithFlags for PaintWorklet

This CL implements the rasterization part for a paint image that is
generated by PaintWorklet, which is the DrawImageOp::RasterWithFlags.

Bug: 907897
Change-Id: I993d29035f1ad09e7cbe3caecc5445876078ac01
Reviewed-on: https://chromium-review.googlesource.com/c/1426015
Reviewed-by: Khushal <khushalsagar@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#633815}
5 files changed