Remove superfluous AnimationController::suspend/resumeAnimations()

These methods were added to provide the embedder (of WebKit) with control over
animations. However, this functionality is not used by Chromium.

The only users of these methods are the corresponding methods on the Internals
testing object, but these exist simply to allow this functionality to be
exercised in tests (https://bugs.webkit.org/show_bug.cgi?id=43733).

Note GraphicsLayer::suspendAnimations() is used by Internals::pauseAnimations(),
so is still required.

This change also removes all of the tests of this functionality, most of which
are either broken or flaky anyway.

A later change to Chromium will remove the implementation of
WebLayer::resumeAnimations(), which is no longer required.

BUG=248938,243353,62138,61739
R=dstockwell@chromium.org, tkent@chromium.org, dstockwell

Review URL: https://codereview.chromium.org/27589003

git-svn-id: svn://svn.chromium.org/blink/trunk@160040 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Web Animations CSS: Support animation of background-image and -webkit-mask-image

background-image is not specified to be animatable however we are still
animating it to support legacy Blink/WebKit behaviour.

This implementation differs from the existing animation engine in the
following ways:
 - Interpolating between different counts of multiple background/mask
images behaves like a repeatable list interpolation.
 - Animating multiple mask images is supported.
 - The presence of keywords in interpolation defaults back to a 50% step
timing function.
The new test is aimed at the new implementation and will fail for the
current implementation, the Web Animation implementation passes the test.

BUG=257591

Review URL: https://codereview.chromium.org/27415003

git-svn-id: svn://svn.chromium.org/blink/trunk@160041 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Refine toRenderSVGResourceContainer()

As other toFooElements do, this patch checks security vulnerability in every use of toRenderSVGResourceContainer.
Plus, small binary size gain on content_shell(linux 64bit release build) by 0.17K
as it removes same function from RenderObject.

Review URL: https://codereview.chromium.org/27648002

git-svn-id: svn://svn.chromium.org/blink/trunk@160042 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add new TraceEvent API in WebKit::Platform.

The new Trace API supports updating an existing TraceEvent's duration
by the TraceEventHandle returned from addTraceEvent() (which is
temporarily named addTraceEventNew).

Will take the following steps to smoothly migrate to the new API:
1. This CL to add the new APIs (new addTraceEvent is named
   addTraceEventNew temporarily);
2. A chromium CL to implement the new APIs;
3. A blink change to use the new APIs and remove the old
   Platform::addTraceEvent();
4. A chromium CL to change the old addTraceEvent to new API and
   implementation;
5. A blink change to rename addTraceEventNew() to addTraceEvent;
6. A chromium CL to remove the temporary addTraceEventNew();

BUG=trace-viewer:487

Review URL: https://codereview.chromium.org/29693007

git-svn-id: svn://svn.chromium.org/blink/trunk@160043 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: [DeprecateAs] for setters

Docs:
https://sites.google.com/a/chromium.org/dev/blink/webidl/blink-idl-extended-attributes#TOC-DeprecateAs-m-a-c-

BUG=239771
NOTRY=true

Review URL: https://codereview.chromium.org/31523002

git-svn-id: svn://svn.chromium.org/blink/trunk@160044 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use DEFINE_CSS_VALUE_TYPE_CASTS() for SVGColor, SVGPaint, and TextCloneCSSValue

SVGColor, SVGPaint and TextCloneCSSValue don't use DEFINE_CSS_VALUE_TYPE_CASTS() yet. It will help to detect bad type casts.


BUG=N/A

Review URL: https://codereview.chromium.org/27183005

git-svn-id: svn://svn.chromium.org/blink/trunk@160045 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Web Animations: Introduce an API for threaded animation.

BUG=

Review URL: https://codereview.chromium.org/28293002

git-svn-id: svn://svn.chromium.org/blink/trunk@160046 bbb929c8-8fbe-4397-9dbb-9b2b20218538
IDL compiler: Simplify [Custom], [CustomSetter] code

Per:
https://codereview.chromium.org/30533002/#msg8

BUG=239771
NOTRY=true

Review URL: https://codereview.chromium.org/31143003

git-svn-id: svn://svn.chromium.org/blink/trunk@160047 bbb929c8-8fbe-4397-9dbb-9b2b20218538