Bug 1514958 [wpt PR 14577] - Plumbing border box through to viz, and adding clip...

Bug 1514958 [wpt PR 14577] - Plumbing border box through to viz, and adding clip rect to backdrop-filter, a=testonly

Automatic update from web-platform-tests
Plumbing border box through to viz, and adding clip rect to backdrop-filter

With this CL, the border box of the element containing backdrop-filter
is plumbed through to viz, so that the backdrop-filter effect can be
properly clipped at the border box of the element itself. This will keep
it from "bleeding" outside to the border rect of the entire layer (including
children).

This should fix most of the reported bugs related to the filtered effect
extending beyond the proper bounds.

Bug: 497522, 813796, 767997, 659501, 632979, 618913, 593307
Change-Id: I5f24ac79053b3779cea128aacabd60f9d66702f4
Reviewed-on: https://chromium-review.googlesource.com/c/1378811
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: vmpstr <vmpstr@chromium.org>
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618358}

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wpt-commits: e95a36a608508cafe6739bda57ba405cc03e04d5
wpt-pr: 14577