Fix rubber-band overhang getting stuck after a fling.

This got broken by: https://chromiumcodereview.appspot.com/24284003

That CL made the code not start the timer under certain cases
when PlatformWheelEventPhaseEnded was received.

This caused a problem with momentum scroll. How that works is
after the regular scroll events are received, including the
PlatformWheelEventPhaseEnded event, then momentum scroll
events start appearing.

The momentum events can then cause overscroll when a fling
happens. However, the cleanup after that was expected to
happen in the snapRubberBand timer launched from the phase
end event (which now wouldn't be getting launched).

This CL fixes the issue by starting the snap rubber band
timer when a momentum scroll starts (if it hasn't been
started during the phase end event).

BUG=290590

Review URL: https://codereview.chromium.org/24486006

git-svn-id: svn://svn.chromium.org/blink/trunk@158576 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Combine MessagePortChannel and PlatformMessagePortChannel into one class

These were historically separated due to WebKit layering concerns.
In Blink, they can be a single, ThreadSafeRefCounted class.

Also get rid of no-op locallyEntangledPort() method which always returned null.

R=abarth

Review URL: https://codereview.chromium.org/25321003

git-svn-id: svn://svn.chromium.org/blink/trunk@158577 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove sync resize event from FrameView::setFrameRect.

This fixes a hang with resize events and seamless iframes that's
showing up on codereview.chromium.org with the rietveld usability
extension installed.

r156320 added this in a patch that was supposed to just be a refactor.
I'm not convinced we want this code. WebKit added it in
http://trac.webkit.org/changeset/149287 and
http://trac.webkit.org/changeset/150011 and updated it to work for
frame flattening (but not seamless!) in
http://trac.webkit.org/changeset/153640.

I don't really understand the changes to fast/forms, but they're just
undoing unexplained changes from r156320.

BUG=282603

Review URL: https://codereview.chromium.org/25092012

git-svn-id: svn://svn.chromium.org/blink/trunk@158578 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Don't call FormAssociatedElement::validity() internally

This saves the malloc cost and the memory usage of the ValidityState
object which just proxys all methods back to the form control. Calling
it internally doesn't make sense.

This saves 19.5k of memory usage on squished presidents which has 10k form
controls and 0.2% of the recalcStyle cost. 1.4% of the recalcStyle time on
that page is spent in malloc, we should drive it down as far as possible.

Review URL: https://codereview.chromium.org/25076008

git-svn-id: svn://svn.chromium.org/blink/trunk@158579 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move the resizer logic to RenderLayerScrollableArea

BUG=260899

Review URL: https://codereview.chromium.org/25140002

git-svn-id: svn://svn.chromium.org/blink/trunk@158580 bbb929c8-8fbe-4397-9dbb-9b2b20218538