Find root scroll layer at tree activation

cc/top_controls_manager.cc

 // Copyright 2013 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/top_controls_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/time.h"
@@ skipping 28 matching lines @@
       previous_root_scroll_offset_(0.f),
       scroll_readjustment_enabled_(false),
       is_showing_animation_(false) {
   CHECK(client_);
 }
 
 TopControlsManager::~TopControlsManager() {
 }
 
 void TopControlsManager::UpdateDrawPositions() {
-  if (!RootScrollLayer())
+  if (!client_->haveRootScrollLayer())
     return;
 
   // If the scroll position has changed underneath us (i.e. a javascript
   // scroll), then simulate a scroll that covers the delta.
   float scroll_total_y = RootScrollLayerTotalScrollY();
   if (scroll_readjustment_enabled_
       && scroll_total_y != previous_root_scroll_offset_) {
     ScrollBy(gfx::Vector2dF(0, scroll_total_y - previous_root_scroll_offset_));
     StartAnimationIfNecessary();
     previous_root_scroll_offset_ = RootScrollLayerTotalScrollY();
@@ skipping 51 matching lines @@
   return pending_delta - applied_delta;
 }
 
 void TopControlsManager::ScrollEnd() {
   StartAnimationIfNecessary();
   previous_root_scroll_offset_ = RootScrollLayerTotalScrollY();
   scroll_readjustment_enabled_ = true;
 }
 
 void TopControlsManager::Animate(base::TimeTicks monotonic_time) {
-  if (!top_controls_animation_ || !RootScrollLayer())
+  if (!top_controls_animation_ || !client_->haveRootScrollLayer())
     return;
 
   double time = (monotonic_time - base::TimeTicks()).InMillisecondsF();
   float new_offset = top_controls_animation_->getValue(time);
   gfx::Vector2dF scroll_vector(0.f, -(new_offset - controls_top_offset_));
   ScrollInternal(scroll_vector);
   client_->setNeedsRedraw();
 
   if ((is_showing_animation_ && new_offset >= 0) ||
       (!is_showing_animation_ && new_offset <= -top_controls_height_)) {
     top_controls_animation_.reset();
     StartAnimationIfNecessary();
   }
 }
 
 void TopControlsManager::ResetAnimations() {
   if (top_controls_animation_)
     top_controls_animation_.reset();
 }
 
-LayerImpl* TopControlsManager::RootScrollLayer() {
-  return client_->activeTree()->root_scroll_layer();
-}
-
 float TopControlsManager::RootScrollLayerTotalScrollY() {
-  LayerImpl* layer = RootScrollLayer();
-  if (!layer)
-    return 0;
-  gfx::Vector2dF scroll_total = layer->scrollOffset() + layer->scrollDelta();
-  return scroll_total.y();
+  return client_->rootScrollLayerTotalScrollY();
 }
 
 void TopControlsManager::SetupAnimation(bool show_controls) {
   top_controls_animation_ = KeyframedFloatAnimationCurve::create();
   double start_time =
       (base::TimeTicks::Now() - base::TimeTicks()).InMillisecondsF();
   top_controls_animation_->addKeyframe(
       FloatKeyframe::create(start_time, controls_top_offset_,
                             scoped_ptr<TimingFunction>()));
   float max_ending_offset = (show_controls ? 1 : -1) * top_controls_height_;
   top_controls_animation_->addKeyframe(
       FloatKeyframe::create(start_time + kShowHideMaxDurationMs,
                             controls_top_offset_ + max_ending_offset,
                             EaseTimingFunction::create()));
   is_showing_animation_ = show_controls;
 }
 
 void TopControlsManager::StartAnimationIfNecessary() {
   float scroll_total_y = RootScrollLayerTotalScrollY();
 
   if (controls_top_offset_ != 0
       && controls_top_offset_ != -top_controls_height_) {
     SetupAnimation(
         controls_top_offset_ >= -(top_controls_height_ * kShowHideThreshold));
     client_->setNeedsRedraw();
   }
 }
 
 }  // namespace cc