[Android]Optimization of scrollbar animation.

cc/layers/scrollbar_layer_impl_base.cc

Index: cc/layers/scrollbar_layer_impl_base.cc
diff --git a/cc/layers/scrollbar_layer_impl_base.cc b/cc/layers/scrollbar_layer_impl_base.cc
index 62b7dee0ad9c297f99d22a4826cdaf498ac21d96..19b5995955ff8fa727e12d075e19defe924c4ab6 100644
--- a/cc/layers/scrollbar_layer_impl_base.cc
+++ b/cc/layers/scrollbar_layer_impl_base.cc
@@ -249,4 +249,16 @@ void ScrollbarLayerImplBase::ScrollbarParametersDidChange() {
   scroll_layer_->SetScrollbarPosition(this, clip_layer_);
 }
 
+bool ScrollbarLayerImplBase::ScrollbarNeedsUpdate(
+    float vertical_adjust,
+    float current_pos,
+    int maximum,
+    float visible_to_total_length_ratio) {
+  if ((vertical_adjust != vertical_adjust_) || (current_pos != current_pos_) ||
+      (maximum != maximum_) ||
+      (visible_to_total_length_ratio != visible_to_total_length_ratio_))
+    return true;
+  return false;
+}
+
 }  // namespace cc