Web Animations: Remove timeLag from Player API and model

API changes are guarded by experimental feature flag. No visible changes to CSS
animations and element.animate.

This is a prototype for behavior we plan to incorporate into the Web Animations
specification:
* startTime is effective start time or NaN when paused or starting
* timeLag is removed

Review URL: https://codereview.chromium.org/365163004

git-svn-id: svn://svn.chromium.org/blink/trunk@178619 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Flush denormals to zero on arm and arm64.

We also slightly refactor the code to make it a little easier to read.

The impact of denormals on arm appear to be much less pronounced than
on x86, but flushing denormals will make arm and x86 results more similar.

This was tested manually by creating a test to check the response of a
lowpass filter to a very small impulse. All values after a certain
point should be zero when denormals are flushed to zero. If denormals
are not flushed, the non-zero output would last much longer.

Verified on Linux, Windows, OSX, and Android that denormals are flushed.

The test is not included; it seems not that important to ensure
denormals are flushed.

BUG=395254

Review URL: https://codereview.chromium.org/402803003

git-svn-id: svn://svn.chromium.org/blink/trunk@178620 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Improve the find word boundary performance

In endWordBoundary case, finding start boundary in findWordBoundary is unnecessary.
So, skip it to improve the find word boundary performance.

Merge from WebKit
https://bugs.webkit.org/show_bug.cgi?id=125619

BUG= 371249

Review URL: https://codereview.chromium.org/268363016

git-svn-id: svn://svn.chromium.org/blink/trunk@178621 bbb929c8-8fbe-4397-9dbb-9b2b20218538