Web Animations API: Avoid style resolution when calling element.animate()

Source/core/animation/StringKeyframe.cpp

 // Copyright 2014 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.
 
 #include "config.h"
 #include "core/animation/StringKeyframe.h"
 
 #include "core/animation/css/CSSAnimations.h"
 #include "core/animation/interpolation/DefaultStyleInterpolation.h"
 #include "core/animation/interpolation/LegacyStyleInterpolation.h"
@@ skipping 92 matching lines @@
     case CSSPropertyMarginTop:
     case CSSPropertyOutlineOffset:
     case CSSPropertyRight:
     case CSSPropertyTop:
     case CSSPropertyVerticalAlign:
     case CSSPropertyWordSpacing:
         if (LengthStyleInterpolation::canCreateFrom(*fromCSSValue) && LengthStyleInterpolation::canCreateFrom(*toCSSValue))
             return LengthStyleInterpolation::create(fromCSSValue, toCSSValue, property, range);
         break;
     default:
+        element->document().updateRenderTreeIfNeeded();
         break;
     }
 
     // FIXME: Remove the use of AnimatableValues, RenderStyles and Elements here.
     // FIXME: Remove this cache
     if (!m_animatableValueCache)
         m_animatableValueCache = StyleResolver::createAnimatableValueSnapshot(*element, property, fromCSSValue);
 
     RefPtrWillBeRawPtr<AnimatableValue> to = StyleResolver::createAnimatableValueSnapshot(*element, property, toCSSValue);
     toStringPropertySpecificKeyframe(end)->m_animatableValueCache = to;
@@ skipping 14 matching lines @@
 }
 
 void StringKeyframe::PropertySpecificKeyframe::trace(Visitor* visitor)
 {
     visitor->trace(m_value);
     visitor->trace(m_animatableValueCache);
     Keyframe::PropertySpecificKeyframe::trace(visitor);
 }
 
 }