Made double-tap zoom work in pinch virtual viewport mode (Chromium-side).

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 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/trees/layer_tree_host_impl.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/basictypes.h"
@@ skipping 2935 matching lines @@
   scroll_info->top_controls_delta = active_tree()->top_controls_delta();
   active_tree_->set_sent_top_controls_delta(scroll_info->top_controls_delta);
 
   return scroll_info.Pass();
 }
 
 void LayerTreeHostImpl::SetFullRootLayerDamage() {
   SetViewportDamage(gfx::Rect(DrawViewportSize()));
 }
 
+void LayerTreeHostImpl::ScrollViewportInnerFirst(gfx::Vector2dF scroll_delta) {
+  DCHECK(InnerViewportScrollLayer());
+  LayerImpl* scroll_layer = InnerViewportScrollLayer();
+
+  gfx::Vector2dF unused_delta = scroll_layer->ScrollBy(scroll_delta);
+  if (!unused_delta.IsZero() && OuterViewportScrollLayer())
+    OuterViewportScrollLayer()->ScrollBy(unused_delta);
+}
+
 void LayerTreeHostImpl::ScrollViewportBy(gfx::Vector2dF scroll_delta) {
   DCHECK(InnerViewportScrollLayer());
   LayerImpl* scroll_layer = OuterViewportScrollLayer()
                                 ? OuterViewportScrollLayer()
                                 : InnerViewportScrollLayer();
 
   gfx::Vector2dF unused_delta = scroll_layer->ScrollBy(scroll_delta);
 
   if (!unused_delta.IsZero() && (scroll_layer == OuterViewportScrollLayer()))
     InnerViewportScrollLayer()->ScrollBy(unused_delta);
 }
 
 void LayerTreeHostImpl::AnimatePageScale(base::TimeTicks monotonic_time) {
   if (!page_scale_animation_)
     return;
 
   gfx::Vector2dF scroll_total = active_tree_->TotalScrollOffset();
 
   if (!page_scale_animation_->IsAnimationStarted())
     page_scale_animation_->StartAnimation(monotonic_time);
 
   active_tree_->SetPageScaleDelta(
       page_scale_animation_->PageScaleFactorAtTime(monotonic_time) /
       active_tree_->page_scale_factor());
   gfx::Vector2dF next_scroll =
       page_scale_animation_->ScrollOffsetAtTime(monotonic_time);
 
-  ScrollViewportBy(next_scroll - scroll_total);
+  ScrollViewportInnerFirst(next_scroll - scroll_total);
   SetNeedsRedraw();
 
   if (page_scale_animation_->IsAnimationCompleteAtTime(monotonic_time)) {
     page_scale_animation_.reset();
     client_->SetNeedsCommitOnImplThread();
     client_->RenewTreePriority();
   } else {
     SetNeedsAnimate();
   }
 }
@@ skipping 389 matching lines @@
 }
 
 void LayerTreeHostImpl::UnregisterPictureLayerImpl(PictureLayerImpl* layer) {
   std::vector<PictureLayerImpl*>::iterator it =
       std::find(picture_layers_.begin(), picture_layers_.end(), layer);
   DCHECK(it != picture_layers_.end());
   picture_layers_.erase(it);
 }
 
 }  // namespace cc