Animation start scale should be considered for the raster scale

cc/animation/animation_curve.h

Index: cc/animation/animation_curve.h
diff --git a/cc/animation/animation_curve.h b/cc/animation/animation_curve.h
index 1074203f239f0f74aac53799bae581089f9cee8f..68bad3ba3b55d5b21699c38d7d9cc14eb70f53c4 100644
--- a/cc/animation/animation_curve.h
+++ b/cc/animation/animation_curve.h
@@ -85,6 +85,10 @@ class CC_EXPORT TransformAnimationCurve : public AnimationCurve {
   // Returns true if this animation preserves axis alignment.
   virtual bool PreservesAxisAlignment() const = 0;
 
+  // Animation start scale
+  virtual bool AnimationStartScale(bool forward_direction,
+                                   float* start_scale) const = 0;
+
   // Set |max_scale| to the maximum scale along any dimension at the end of
   // intermediate animation target points (eg keyframe end points). When
   // |forward_direction| is true, the animation curve assumes it plays from