Make stacking order RenderLayer tree the same regardless of compositing mode.

The compositor is always checking for udpates even when compositing mode
is disabled. However, the stacking order tree (input to the compositing
code) was ommitting visible:hidden layers when compositing mode
is disabled. This inconsistency needs to be fixed to enable upcoming
changes without breaking assumptions.

Most rebaselines are included in the patch, but a few are left
for the gardening tools to auto rebaseline.

BUG=325987

Review URL: https://codereview.chromium.org/109803004

git-svn-id: svn://svn.chromium.org/blink/trunk@163715 bbb929c8-8fbe-4397-9dbb-9b2b20218538