CustomButton: restrict animation repaints to buttons that actually animate

ui/views/controls/button/custom_button.h

Index: ui/views/controls/button/custom_button.h
diff --git a/ui/views/controls/button/custom_button.h b/ui/views/controls/button/custom_button.h
index a73d5008cf67e90ce6790de0f9bca7660573736c..161824c9869e35bbcdfbbadd62dd258d932d7a0f 100644
--- a/ui/views/controls/button/custom_button.h
+++ b/ui/views/controls/button/custom_button.h
@@ -42,6 +42,7 @@ class VIEWS_EXPORT CustomButton : public Button, public gfx::AnimationDelegate {
   void SetState(ButtonState state);
 
   // Starts throbbing. See HoverAnimation for a description of cycles_til_stop.
+  // This method does nothing if |animate_on_state_change_| is false.
   void StartThrobbing(int cycles_til_stop);
 
   // Stops throbbing immediately.
@@ -165,8 +166,8 @@ class VIEWS_EXPORT CustomButton : public Button, public gfx::AnimationDelegate {
 
   gfx::ThrobAnimation hover_animation_;
 
-  // Should we animate when the state changes? Defaults to true.
-  bool animate_on_state_change_;
+  // Should we animate when the state changes?
+  bool animate_on_state_change_ = false;
 
   // Is the hover animation running because StartThrob was invoked?
   bool is_throbbing_;