Have Frame::animation() return a reference

Source/core/rendering/CompositedLayerMapping.cpp

Index: Source/core/rendering/CompositedLayerMapping.cpp
diff --git a/Source/core/rendering/CompositedLayerMapping.cpp b/Source/core/rendering/CompositedLayerMapping.cpp
index 22847d5f0893c20e649a990ff0b8ea324666a206..d34b2c3e0ef4712a8cc5884890b7219da67d3af4 100644
--- a/Source/core/rendering/CompositedLayerMapping.cpp
+++ b/Source/core/rendering/CompositedLayerMapping.cpp
@@ -512,11 +512,11 @@ void CompositedLayerMapping::updateGraphicsLayerGeometry()
 
     // Set transform property, if it is not animating. We have to do this here because the transform
     // is affected by the layer dimensions.
-    if (!renderer()->animation()->isRunningAcceleratedAnimationOnRenderer(renderer(), CSSPropertyWebkitTransform))
+    if (!renderer()->animation().isRunningAcceleratedAnimationOnRenderer(renderer(), CSSPropertyWebkitTransform))
         updateTransform(renderer()->style());
 
     // Set opacity, if it is not animating.
-    if (!renderer()->animation()->isRunningAcceleratedAnimationOnRenderer(renderer(), CSSPropertyOpacity))
+    if (!renderer()->animation().isRunningAcceleratedAnimationOnRenderer(renderer(), CSSPropertyOpacity))
         updateOpacity(renderer()->style());
 
     if (RuntimeEnabledFeatures::cssCompositingEnabled())
@@ -1885,7 +1885,7 @@ void CompositedLayerMapping::transitionFinished(CSSPropertyID property)
 
 void CompositedLayerMapping::notifyAnimationStarted(const GraphicsLayer*, double time)
 {
-    renderer()->animation()->notifyAnimationStarted(renderer(), time);
+    renderer()->animation().notifyAnimationStarted(renderer(), time);
 }
 
 // This is used for the 'freeze' API, for testing only.