[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"
 
 namespace cc {
 
 ScrollbarLayerImplBase::ScrollbarLayerImplBase(
     LayerTreeImpl* tree_impl,
     int id,
     ScrollbarOrientation orientation,
     bool is_left_side_vertical_scrollbar,
     bool is_overlay)
     : LayerImpl(tree_impl, id),
       scroll_layer_(NULL),
       clip_layer_(NULL),
       is_overlay_scrollbar_(is_overlay),
       thumb_thickness_scale_factor_(1.f),
       current_pos_(0.f),
       maximum_(0),
       orientation_(orientation),
       is_left_side_vertical_scrollbar_(is_left_side_vertical_scrollbar),
       vertical_adjust_(0.f),
-      visible_to_total_length_ratio_(1.f) {}
+      visible_to_total_length_ratio_(1.f),
+      scrollbar_needs_animation_(false) {
+}
 
 ScrollbarLayerImplBase::~ScrollbarLayerImplBase() {}
 
 void ScrollbarLayerImplBase::PushPropertiesTo(LayerImpl* layer) {
   float active_opacity = layer->opacity();
   LayerImpl::PushPropertiesTo(layer);
   layer->SetOpacity(active_opacity);
   DCHECK(layer->ToScrollbarLayer());
   layer->ToScrollbarLayer()->set_is_overlay_scrollbar(is_overlay_scrollbar_);
   PushScrollClipPropertiesTo(layer);
@@ skipping 62 matching lines @@
   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) {
   if (current_pos_ == current_pos)
     return;
   current_pos_ = current_pos;
+  scrollbar_needs_animation_ = true;
   NoteLayerPropertyChanged();
 }
 
 void ScrollbarLayerImplBase::SetMaximum(int maximum) {
   if (maximum_ == maximum)
     return;
   maximum_ = maximum;
+  scrollbar_needs_animation_ = true;
   NoteLayerPropertyChanged();
 }
 
 void ScrollbarLayerImplBase::SetVerticalAdjust(float vertical_adjust) {
   if (vertical_adjust_ == vertical_adjust)
     return;
   vertical_adjust_ = vertical_adjust;
+  scrollbar_needs_animation_ = true;
   NoteLayerPropertyChanged();
 }
 
 void ScrollbarLayerImplBase::SetVisibleToTotalLengthRatio(float ratio) {
   if (!IsThumbResizable())
     return;
 
   if (visible_to_total_length_ratio_ == ratio)
     return;
   visible_to_total_length_ratio_ = ratio;
+  scrollbar_needs_animation_ = true;
   NoteLayerPropertyChanged();
 }
 
 void ScrollbarLayerImplBase::SetThumbThicknessScaleFactor(float factor) {
   if (thumb_thickness_scale_factor_ == factor)
     return;
   thumb_thickness_scale_factor_ = factor;
+  scrollbar_needs_animation_ = true;
   NoteLayerPropertyChanged();
 }
 
 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 90 matching lines @@
 }
 
 void ScrollbarLayerImplBase::ScrollbarParametersDidChange() {
   if (!clip_layer_ || !scroll_layer_)
     return;
 
   scroll_layer_->SetScrollbarPosition(this, clip_layer_);
 }
 
 }  // namespace cc