Do not squash layers with inherited opacity, transform, or filters.

These are all properties that require that the descendant paints into
the same composited layer as the ancestor, so squashing breaks rendering.
Most of the included layout tests, plus
compositing/geometry/video-opacity-overlay.html, fail before this patch
when squashing is turned on.

Note that reflection, blending, and mask, despite being reasons to promote
the ancestor, appear to already work the same way with or without squashing.
As such, I haven't added in any code to handle those properties, but I did
add some extra layout tests to make sure they remain correct.

BUG=361218

Review URL: https://codereview.chromium.org/231573002

git-svn-id: svn://svn.chromium.org/blink/trunk@171309 bbb929c8-8fbe-4397-9dbb-9b2b20218538