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Reland of "Mustash: Ensure surfaces submitted to Mus by WM and embedders contain Surfaces with embeded content."

- Use SurfaceLayers in embedders and Window Manager to properly position
  the embedded content in the layer tree.

- WM no longer uses underlay surfaces for window decorations. Instead
  they are submitted to Mus as part of the WM's surface.

- FrameGenerator now only creates SurfaceDrawQuad for the top-level
  window rather than recursively creating SurfaceDrawQuad for all windows
  in the window tree, since all surfaces are now part of the tree rooted
  at the surface of the top-level window.

Previously landed in crrev.com/441492, but reverted in crrev.com/441522
since it broke some tests on Windows. This CL includes a fix for that
brokenness.

BUG=672943, 669964
TBR=jbauman@ for DEPS change (previously lgtm'ed in the original CL)

Review-Url: https://codereview.chromium.org/2613903003
Cr-Commit-Position: refs/heads/master@{#441753}