Implement fade-out animation for Aura overlay scrollbars (CC only).

cc/input/scrollbar_animation_controller_linear_fade.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/input/scrollbar_animation_controller_linear_fade.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/time/time.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/scrollbar_layer_impl_base.h"
@@ skipping 15 matching lines @@
 
 ScrollbarAnimationControllerLinearFade::ScrollbarAnimationControllerLinearFade(
     int scroll_layer_id,
     ScrollbarAnimationControllerClient* client,
     base::TimeDelta delay_before_starting,
     base::TimeDelta resize_delay_before_starting,
     base::TimeDelta duration)
     : ScrollbarAnimationController(scroll_layer_id,
                                    client,
                                    delay_before_starting,
-                                   resize_delay_before_starting,
-                                   duration) {}
+                                   resize_delay_before_starting),
+      duration_(duration) {}
 
 ScrollbarAnimationControllerLinearFade::
     ~ScrollbarAnimationControllerLinearFade() {}
 
 void ScrollbarAnimationControllerLinearFade::RunAnimationFrame(float progress) {
   ApplyOpacityToScrollbars(1.f - progress);
   client_->SetNeedsRedrawForScrollbarAnimation();
   if (progress == 1.f)
     StopAnimation();
 }
 
+const base::TimeDelta& ScrollbarAnimationControllerLinearFade::Duration() {
+  return duration_;
+}
+
 void ScrollbarAnimationControllerLinearFade::DidScrollUpdate(bool on_resize) {
   ScrollbarAnimationController::DidScrollUpdate(on_resize);
   ApplyOpacityToScrollbars(1.f);
 }
 
 void ScrollbarAnimationControllerLinearFade::ApplyOpacityToScrollbars(
     float opacity) {
   for (ScrollbarLayerImplBase* scrollbar : Scrollbars()) {
     if (!scrollbar->is_overlay_scrollbar())
       continue;
     PropertyTrees* property_trees =
         scrollbar->layer_tree_impl()->property_trees();
     // If this method is called during LayerImpl::PushPropertiesTo, we may not
     // yet have valid effect_id_to_index_map entries as property trees are
     // pushed after layers during activation. We can skip updating opacity in
     // that case as we are only registering a scrollbar and because opacity will
     // be overwritten anyway when property trees are pushed.
     if (property_trees->IsInIdToIndexMap(PropertyTrees::TreeType::EFFECT,
                                          scrollbar->id())) {
       property_trees->effect_tree.OnOpacityAnimated(
           scrollbar->CanScrollOrientation() ? opacity : 0,
           property_trees->effect_id_to_index_map[scrollbar->id()],
           scrollbar->layer_tree_impl());
     }
   }
 }
 
 }  // namespace cc