[Android]Optimization of scrollbar animation.

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 5b39eb0e36262c2299be2fd73522def8ab8c897c..a7569675060739584fa3506d1ad410d048a14f8c 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -1274,7 +1274,7 @@ void LayerImpl::SetScrollbarPosition(ScrollbarLayerImplBase* scrollbar_layer,
     scroll_rect.Scale(layer_tree_impl()->total_page_scale_factor());
     current_offset.Scale(layer_tree_impl()->total_page_scale_factor());
   }
-
+  scrollbar_layer->ResetScrollbarNeedsAnimation();
   scrollbar_layer->SetVerticalAdjust(scrollbar_clip_layer->bounds_delta().y());
   if (scrollbar_layer->orientation() == HORIZONTAL) {
     float visible_ratio = clip_rect.width() / scroll_rect.width();
@@ -1299,6 +1299,7 @@ void LayerImpl::SetScrollbarPosition(ScrollbarLayerImplBase* scrollbar_layer,
     // Non-overlay scrollbars also shouldn't trigger animations.
     bool is_animatable_scrollbar =
         scrollbar_layer->is_overlay_scrollbar() &&
+        scrollbar_layer->scrollbar_needs_animation() &&

[danakj, 2014/09/19 23:01:35]

remove this here, it's not part of |is_animatable_scrollbar|

         ((layer_tree_impl()->total_page_scale_factor() >
           layer_tree_impl()->min_page_scale_factor()) ||
          !layer_tree_impl()->settings().use_pinch_zoom_scrollbars);