[Sketch] Animations: Torpedo the old intrusive animation system.

Source/platform/graphics/GraphicsLayerClient.h

Index: Source/platform/graphics/GraphicsLayerClient.h
diff --git a/Source/platform/graphics/GraphicsLayerClient.h b/Source/platform/graphics/GraphicsLayerClient.h
index ea4ccd2cdda51045b2943d2f04e34cb7fb8d8ce0..568100f6b960593e46b2bc416f8f0fd0c78a7422 100644
--- a/Source/platform/graphics/GraphicsLayerClient.h
+++ b/Source/platform/graphics/GraphicsLayerClient.h
@@ -62,9 +62,6 @@ class PLATFORM_EXPORT GraphicsLayerClient {
 public:
     virtual ~GraphicsLayerClient() {}
 
-    // Callback for when compositor animation started.
-    virtual void notifyAnimationStarted(const GraphicsLayer*, double monotonicTime, int group) { };
-
     virtual void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect& inClip) = 0;
     virtual bool isTrackingPaintInvalidations() const { return false; }