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Previous CL's have added information regarding an image's origin and
alpha type to SharedImageBacking. This CL uses that info in place of
assumed defaults when creating SkSurfaces for write access.

Bug: 1034086
Change-Id: I82f1a400acc09724b0667318a34208ebeb91d549
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2307533
Commit-Queue: Nathan Zabriskie <nazabris@microsoft.com>
Reviewed-by: Khushal <khushalsagar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790239}