Disable overlay scrollbars in Blink when hidden by the compositor.

cc/input/scrollbar_animation_controller.cc

Index: cc/input/scrollbar_animation_controller.cc
diff --git a/cc/input/scrollbar_animation_controller.cc b/cc/input/scrollbar_animation_controller.cc
index 086f63e30f939ef11c662d500b9bf51c2f3899a0..a29708d411754d29d608b2bb49b50a2abd875131 100644
--- a/cc/input/scrollbar_animation_controller.cc
+++ b/cc/input/scrollbar_animation_controller.cc
@@ -17,10 +17,10 @@ ScrollbarAnimationController::ScrollbarAnimationController(
     base::TimeDelta delay_before_starting,
     base::TimeDelta resize_delay_before_starting)
     : client_(client),
+      scroll_layer_id_(scroll_layer_id),
       delay_before_starting_(delay_before_starting),
       resize_delay_before_starting_(resize_delay_before_starting),
       is_animating_(false),
-      scroll_layer_id_(scroll_layer_id),
       currently_scrolling_(false),
       scroll_gesture_has_scrolled_(false),
       weak_factory_(this) {}