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|intersects_damage_under|.

The |can_use_cached_backdrop_filtered_result_| flag on a
|RenderSurfaceImpl| is set during damage tracking to mark if there's
any intersecting damage from layers or other render surfaces under this
|RenderSurfaceImpl| rendering to the same target.

Previously this flag was intended only for a render surface with a
backdrop filter to avoid recomputation of the backdrop filter, i.e. to
use cached result, if there was no intersecting damage from under it. As
this flag is already on |RenderSurfaceImpl|, we can use it for a more
general purpose optimization at a later stage (during surface
aggregation) in the pipeline if we set it appropriately for every render
surface, with or without a backdrop filter.

Bug: 1142892
Change-Id: Icc0e418bc4f7c09bb2825dc21fb1f8706ebcf64a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2538957Reviewed-by: weiliangc <weiliangc@chromium.org>
Commit-Queue: Jun Liu <yjliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827822}