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This CL reworks PaintChunksToCcLayer to handle effect grouping properly.

Prior to this CL each paint chunk applies its property state all the way from the
layer state then pop all the way back. This CL implemented an algorithm to lazily
pop states so that contiguous paint chunks enclosed by the same effect will apply
the effect atomically.

As an optimization, clip region is also popped lazily. Note that this doesn't mean
AA-clips are applied as a group but still apply to individual draw commands
separately. It does improve performance by reusing previously generated clip region
when a complex clip region applies to multiple chunks repeatedly. Rounded clip
support is also added as a side change.

Transforms are always applied on the spot. This is because we can compute the
matrix between arbitrary nodes in O(1). Also this automatically handles "transform
inversion" cases as we don't even need to detect the relationship between nodes.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I64657b657fad3e19132b9eb0d64db494955f2139
Reviewed-on: https://chromium-review.googlesource.com/540737
Commit-Queue: Tien-Ren Chen <trchen@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485109}