[Android]Optimization of scrollbar animation.

cc/layers/layer_impl.cc

 // Copyright 2012 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/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/debug/trace_event_argument.h"
 #include "base/json/json_reader.h"
 #include "base/strings/stringprintf.h"
@@ skipping 1257 matching lines @@
   }
   // TODO(wjmaclean) Once we move to a model where the two-viewport model is
   // turned on in all builds, remove the next two lines. For now however, the
   // page scale layer may coincide with the clip layer, and so this is
   // necessary.
   if (page_scale_layer == scrollbar_clip_layer) {
     scroll_rect.Scale(layer_tree_impl()->total_page_scale_factor());
     current_offset.Scale(layer_tree_impl()->total_page_scale_factor());
   }
 
-  scrollbar_layer->SetVerticalAdjust(scrollbar_clip_layer->bounds_delta().y());
+  bool scrollbar_needs_animation = false;
+  scrollbar_needs_animation = scrollbar_layer->SetVerticalAdjust(
+      scrollbar_clip_layer->bounds_delta().y());
   if (scrollbar_layer->orientation() == HORIZONTAL) {
     float visible_ratio = clip_rect.width() / scroll_rect.width();
-    scrollbar_layer->SetCurrentPos(current_offset.x());
-    scrollbar_layer->SetMaximum(scroll_rect.width() - clip_rect.width());
-    scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
+    scrollbar_needs_animation =

[aelias_OOO_until_Jul13, 2014/09/22 06:53:01]

This will reset to false if any later line is false.  Use |= in all these lines.

[MuVen, 2014/09/22 14:02:27]

True, MissRead the logic :( Done.

+        scrollbar_layer->SetCurrentPos(current_offset.x());
+    scrollbar_needs_animation =
+        scrollbar_layer->SetMaximum(scroll_rect.width() - clip_rect.width());
+    scrollbar_needs_animation =
+        scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
   } else {
     float visible_ratio = clip_rect.height() / scroll_rect.height();
-    scrollbar_layer->SetCurrentPos(current_offset.y());
-    scrollbar_layer->SetMaximum(scroll_rect.height() - clip_rect.height());
-    scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
+    scrollbar_needs_animation =
+        scrollbar_layer->SetCurrentPos(current_offset.y());
+    scrollbar_needs_animation =
+        scrollbar_layer->SetMaximum(scroll_rect.height() - clip_rect.height());
+    scrollbar_needs_animation =
+        scrollbar_layer->SetVisibleToTotalLengthRatio(visible_ratio);
   }
 
   layer_tree_impl()->set_needs_update_draw_properties();
   // TODO(wjmaclean) The scrollbar animator for the pinch-zoom scrollbars should
   // activate for every scroll on the main frame, not just the scrolls that move
   // the pinch virtual viewport (i.e. trigger from either inner or outer
   // viewport).
-  if (scrollbar_animation_controller_) {
+  if (scrollbar_animation_controller_ && scrollbar_needs_animation) {
     // When both non-overlay and overlay scrollbars are both present, don't
     // animate the overlay scrollbars when page scale factor is at the min.
     // Non-overlay scrollbars also shouldn't trigger animations.
     bool is_animatable_scrollbar =
         scrollbar_layer->is_overlay_scrollbar() &&
         ((layer_tree_impl()->total_page_scale_factor() >
           layer_tree_impl()->min_page_scale_factor()) ||
          !layer_tree_impl()->settings().use_pinch_zoom_scrollbars);
     if (is_animatable_scrollbar)
       scrollbar_animation_controller_->DidScrollUpdate();
@@ skipping 231 matching lines @@
 }
 
 void LayerImpl::NotifyAnimationFinished(
     base::TimeTicks monotonic_time,
     Animation::TargetProperty target_property) {
   if (target_property == Animation::ScrollOffset)
     layer_tree_impl_->InputScrollAnimationFinished();
 }
 
 }  // namespace cc