[Android]Optimization of scrollbar animation.

cc/layers/scrollbar_layer_impl_base.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/layers/scrollbar_layer_impl_base.h"
 
 #include <algorithm>
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/rect_conversions.h"
 
@@ skipping 87 matching lines @@
 gfx::Rect ScrollbarLayerImplBase::ScrollbarLayerRectToContentRect(
     const gfx::RectF& layer_rect) const {
   // Don't intersect with the bounds as in LayerRectToContentRect() because
   // layer_rect here might be in coordinates of the containing layer.
   gfx::RectF content_rect = gfx::ScaleRect(layer_rect,
       contents_scale_x(),
       contents_scale_y());
   return gfx::ToEnclosingRect(content_rect);
 }
 
-void ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
+bool ScrollbarLayerImplBase::SetCurrentPos(float current_pos) {
   if (current_pos_ == current_pos)
-    return;
+    return false;
   current_pos_ = current_pos;
   NoteLayerPropertyChanged();
+  return true;
 }
 
-void ScrollbarLayerImplBase::SetMaximum(int maximum) {
+bool ScrollbarLayerImplBase::SetMaximum(int maximum) {
   if (maximum_ == maximum)
-    return;
+    return false;
   maximum_ = maximum;
   NoteLayerPropertyChanged();
+  return true;
 }
 
-void ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
+bool ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
   if (vertical_adjust_ == vertical_adjust)
-    return;
+    return false;
   vertical_adjust_ = vertical_adjust;
   NoteLayerPropertyChanged();
+  return true;
 }
 
-void ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
+bool ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
   if (!IsThumbResizable())
-    return;
+    return false;
 
   if (visible_to_total_length_ratio_ == ratio)
-    return;
+    return false;
   visible_to_total_length_ratio_ = ratio;
   NoteLayerPropertyChanged();
+  return true;
 }
 
-void ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
+bool ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
   if (thumb_thickness_scale_factor_ == factor)
-    return;
+    return false;
   thumb_thickness_scale_factor_ = factor;
   NoteLayerPropertyChanged();
+  return true;
 }
 
 gfx::Rect ScrollbarLayerImplBase::ComputeThumbQuadRect() const {
   // Thumb extent is the length of the thumb in the scrolling direction, thumb
   // thickness is in the perpendicular direction. Here's an example of a
   // horizontal scrollbar - inputs are above the scrollbar, computed values
   // below:
   //
   //    |<------------------- track_length_ ------------------->|
   //
@@ skipping 89 matching lines @@
 }
 
 void ScrollbarLayerImplBase::ScrollbarParametersDidChange() {
   if (!clip_layer_ || !scroll_layer_)
     return;
 
   scroll_layer_->SetScrollbarPosition(this, clip_layer_);
 }
 
 }  // namespace cc