Ignore should-scroll-on-main-thread if main frame is not scrollable

The reasons for forcing main frame scrolling are applicable for main frame
scrolling. If we are not scrolling the main frame (and scrolling cannot bubble
to the main frame), we should ignore this hint.

R=aelias@chromium.org,jamesr@chromium.org
BUG=254435

Review URL: https://chromiumcodereview.appspot.com/22694003

git-svn-id: svn://svn.chromium.org/blink/trunk@156727 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove use of <memory> include from Blink headers.

It's aspecific, pulls in a lot of heavy include work, and does not seem to be
necessary.

Review URL: https://chromiumcodereview.appspot.com/23443002

git-svn-id: svn://svn.chromium.org/blink/trunk@156728 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove dead OpenType code

Also remove a bit of the exclude pattern for OpenType in core.gyp,
since it never matched anything: the exclusion is instead taken
care of by the directory exclude line.

R=abarth

Review URL: https://chromiumcodereview.appspot.com/23011052

git-svn-id: svn://svn.chromium.org/blink/trunk@156729 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Promote all siblings after an unclipped descendant in stacking order.

We don't overlap test during impl scrolling. To ensure we
don't get incorrect behavior, we must promote layers that
could potentially promote due to overlap during a scroll. To
fix this, we also have to go ahead and promote any layer
that is a sibling of an unclipped descendant, and also comes
after the unclipped descendant in stacking order, just in
case they may overlap during the scroll.

This is blink-side patch 3 of https://docs.google.com/a/chromium.org/document/d/1Ln57_v6_4RmuuvtWnpsfBOUeDFrPsYNFW13dwuQ8UD8.

BUG=

Review URL: https://chromiumcodereview.appspot.com/22381008

git-svn-id: svn://svn.chromium.org/blink/trunk@156730 bbb929c8-8fbe-4397-9dbb-9b2b20218538