Animation start scale should be considered for the raster scale

cc/animation/layer_animation_controller.h

Index: cc/animation/layer_animation_controller.h
diff --git a/cc/animation/layer_animation_controller.h b/cc/animation/layer_animation_controller.h
index d459515f5df365f3d68f96f3e4b571881d289656..1ac76fa393ed5ad60102ae50365303a7b0b3f649 100644
--- a/cc/animation/layer_animation_controller.h
+++ b/cc/animation/layer_animation_controller.h
@@ -134,6 +134,11 @@ class CC_EXPORT LayerAnimationController
 
   bool AnimationsPreserveAxisAlignment() const;
 
+  // Sets |start_scale| to the maximum of starting animation scale along any
+  // dimension at any destination in active animations. Returns false if the
+  // starting scale cannot be computed.
+  bool AnimationStartScale(float* start_scale) const;
+
   // Sets |max_scale| to the maximum scale along any dimension at any
   // destination in active animations. Returns false if the maximum scale cannot
   // be computed.