--disable-layer-squashing should disable layer squashing

To avoid complicated three-sided CLs to enable layer squashing, we hard-enabled
squashing yesterday. Now that all the repos have caught up to each other, we
can connect --disable-layer-squashing to actually control whether layer
squashing is enabled.

R=chrishtr@chromium.org

Review URL: https://codereview.chromium.org/245563007

git-svn-id: svn://svn.chromium.org/blink/trunk@172085 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix repaint in sub-pixel composited layers

Prior to properly accumulating sub-pixel offsets through composited layers,
there was a hack in RenderLayerRepainter to adjust repaint rects by the
sub-pixel accumulation. Now that this accumulation is properly handled in
the rest of the stack, this is no longer needed, and instead results in us
applying the sub-pixel offset twice (we'll do it again at paint-time).

BUG=362938

Review URL: https://codereview.chromium.org/244523006

git-svn-id: svn://svn.chromium.org/blink/trunk@172086 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve unprefixed MediaSource test coverage.

These changes add test cases for the unprefixed MediaSource API that are
derived from the existing prefixed MediaSource tests. These are being
added so that we don't lose test coverage when the prefixed API and
tests are removed.

BUG=363444

Review URL: https://codereview.chromium.org/245893002

git-svn-id: svn://svn.chromium.org/blink/trunk@172087 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Update VS2013 test expectations

Remove stale NeedsManualRebaseline expecations since VS2013 migration
and skip audio tests on win debug.

BUG=309197
TBR=scottmg@chromium.org

Review URL: https://codereview.chromium.org/245913002

git-svn-id: svn://svn.chromium.org/blink/trunk@172090 bbb929c8-8fbe-4397-9dbb-9b2b20218538