Add AnimationTimingProperties dictionary

Source/core/animation/AnimationTimingProperties.idl

-// Copyright 2014 The Chromium Authors. All rights reserved.
+// Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// FIXME: Should extend AnimationTimingProperties
 [
     TypeChecking=Unrestricted,
-] dictionary ComputedTimingProperties {
-    double              startTime;
-    unrestricted double endTime;
-    unrestricted double activeDuration;
-    double?             localTime;
-    unrestricted double timeFraction;
-    unsigned long?      currentIteration;
-
-    // FIXME: These should be inherited from AnimationTimingProperties
+] dictionary AnimationTimingProperties {
     double                             delay = 0;
     double                             endDelay = 0;
     DOMString                          fill = "auto";
     double                             iterationStart = 0.0;
     unrestricted double                iterations = 1.0;
-    // FIXME: Default should be 'auto'
-    (unrestricted double or DOMString) duration;
+    (unrestricted double or DOMString) duration = "auto";
     double                             playbackRate = 1.0;
     DOMString                          direction = "normal";
     DOMString                          easing = "linear";
 };