Don't synchronize attributes unless necessary when matching
attribute CSS selectors.

Previously, synchronization was always happening, causing a
large performance impact due to syncing of inline styles
into the "style" attribute on some pages that updated
styles on every frame.

Fix another small bug in which the two versions of synchronizeAttribute in the Element class were not functionally equivalent (in particular, with regard to case-sensitive matching on the style attribute).

BUG=322239

Review URL: https://codereview.chromium.org/100433003

git-svn-id: svn://svn.chromium.org/blink/trunk@163464 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix duplicate timeupdate events

This change prevents duplicate timeupdate events caused by the text
track code. The comment above the call indicates that the timeupdate
event should have the same restrictions as the normal periodic
timeupdate event. By changing the parameter passed to
scheduleTimeupdateEvent() to true, the event rate limiting guards
are properly applied to this call and duplicate events won't
fire.

TEST=Manually tested that timeupdate events don't fire more
often than every 250ms during normal playback. An automated
test to verify this would likely be flaky.

Review URL: https://codereview.chromium.org/108253006

git-svn-id: svn://svn.chromium.org/blink/trunk@163465 bbb929c8-8fbe-4397-9dbb-9b2b20218538
This refactoring removes the logic for bubbling scrolls and moves it up into EventHandler. It also removes the logicalScroll method on RenderBox and also moves that concept into EventHandler, making the scroll method in RenderBox essentially plumbing to the associated ScrollableArea. This puts most of scrolling logic in one place and makes further cleanup possible.

BUG=325554

Review URL: https://codereview.chromium.org/102983002

git-svn-id: svn://svn.chromium.org/blink/trunk@163466 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove UnusedParam.h as most of its use is not not needed.

Chromium and Blink sets -Wno-unused-parameter intentionally, so no need to silence related warnings using the UNUSED_PARAM macro. 

Introduce ALLOW_UNUSED for Blink to mark local variables that might be unused to silence -Wunused-variable. The same macro exists on the chromium side with the same definition.

Replace UNUSED_PARAM with the newly introduced ALLOW_UNUSED where needed.

TBR=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/34273002

git-svn-id: svn://svn.chromium.org/blink/trunk@163467 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Test for https://src.chromium.org/viewvc/blink?revision=163447&view=revision

This covers the case where an iframe initially loads about:blank, navigates
again to about:blank, then does a real navigation. We were incorrectly creating
a new history entry for the final navigation. The entire operation should
constitute a single entry.

BUG=323574

Review URL: https://codereview.chromium.org/106983008

git-svn-id: svn://svn.chromium.org/blink/trunk@163468 bbb929c8-8fbe-4397-9dbb-9b2b20218538