Note scrollbar layer properties changed when position changes.

cc/layers/scrollbar_layer_impl.cc

Index: cc/layers/scrollbar_layer_impl.cc
diff --git a/cc/layers/scrollbar_layer_impl.cc b/cc/layers/scrollbar_layer_impl.cc
index 51dbe072c4f90cc4d6dff95f10a0f652568204f7..c326d42ff2490e7b4058b764fd25cb855596c0a5 100644
--- a/cc/layers/scrollbar_layer_impl.cc
+++ b/cc/layers/scrollbar_layer_impl.cc
@@ -63,10 +63,10 @@ void ScrollbarLayerImpl::PushPropertiesTo(LayerImpl* layer) {
 
   ScrollbarLayerImpl* scrollbar_layer = static_cast<ScrollbarLayerImpl*>(layer);
 
-  scrollbar_layer->set_thumb_thickness(thumb_thickness_);
-  scrollbar_layer->set_thumb_length(thumb_length_);
-  scrollbar_layer->set_track_start(track_start_);
-  scrollbar_layer->set_track_length(track_length_);
+  scrollbar_layer->SetThumbThickness(thumb_thickness_);
+  scrollbar_layer->SetThumbLength(thumb_length_);
+  scrollbar_layer->SetTrackStart(track_start_);
+  scrollbar_layer->SetTrackLength(track_length_);
   scrollbar_layer->set_is_overlay_scrollbar(is_overlay_scrollbar_);
 
   scrollbar_layer->set_track_ui_resource_id(track_ui_resource_id_);
@@ -169,6 +169,61 @@ gfx::Rect ScrollbarLayerImpl::ScrollbarLayerRectToContentRect(
   return gfx::ToEnclosingRect(content_rect);
 }
 
+void ScrollbarLayerImpl::SetThumbThickness(int thumb_thickness) {
+  if (thumb_thickness_ == thumb_thickness)
+    return;
+  thumb_thickness_ = thumb_thickness;
+  NoteLayerPropertyChanged();
+}
+
+void ScrollbarLayerImpl::SetThumbLength(int thumb_length) {
+  if (thumb_length_ == thumb_length)
+    return;
+  thumb_length_ = thumb_length;
+  NoteLayerPropertyChanged();
+}
+void ScrollbarLayerImpl::SetTrackStart(int track_start) {
+  if (track_start_ == track_start)
+    return;
+  track_start_ = track_start;
+  NoteLayerPropertyChanged();
+}
+
+void ScrollbarLayerImpl::SetTrackLength(int track_length) {
+  if (track_length_ == track_length)
+    return;
+  track_length_ = track_length;
+  NoteLayerPropertyChanged();
+}
+
+void ScrollbarLayerImpl::SetVerticalAdjust(float vertical_adjust) {
+  if (vertical_adjust_ == vertical_adjust)
+    return;
+  vertical_adjust_ = vertical_adjust;
+  NoteLayerPropertyChanged();
+}
+
+void ScrollbarLayerImpl::SetVisibleToTotalLengthRatio(float ratio) {
+  if (visible_to_total_length_ratio_ == ratio)
+    return;
+  visible_to_total_length_ratio_ = ratio;
+  NoteLayerPropertyChanged();
+}
+
+void ScrollbarLayerImpl::SetCurrentPos(float current_pos) {
+  if (current_pos_ == current_pos)
+    return;
+  current_pos_ = current_pos;
+  NoteLayerPropertyChanged();
+}
+
+void ScrollbarLayerImpl::SetMaximum(int maximum) {
+  if (maximum_ == maximum)
+    return;
+  maximum_ = maximum;
+  NoteLayerPropertyChanged();
+}
+
 gfx::Rect ScrollbarLayerImpl::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