Add viewport scrollbar class to support overlay scrollbars for pinch zoom virtual viewport.

cc/trees/layer_tree_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_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/animation/keyframed_animation_curve.h"
 #include "cc/animation/scrollbar_animation_controller.h"
 #include "cc/debug/traced_value.h"
@@ skipping 93 matching lines @@
 
 void LayerTreeImpl::PushPropertiesTo(LayerTreeImpl* target_tree) {
   target_tree->SetLatencyInfo(latency_info_);
   latency_info_.Clear();
   target_tree->SetPageScaleFactorAndLimits(
       page_scale_factor(), min_page_scale_factor(), max_page_scale_factor());
   target_tree->SetPageScaleDelta(
       target_tree->page_scale_delta() / target_tree->sent_page_scale_delta());
   target_tree->set_sent_page_scale_delta(1);
 
+  if (settings().use_pinch_virtual_viewport)
+    target_tree->SetPinchViewportLayerIds(page_scale_layer_->id(),
+                                          inner_viewport_scroll_layer_->id(),
+                                          outer_viewport_scroll_layer_->id());
+
   // This should match the property synchronization in
   // LayerTreeHost::finishCommitOnImplThread().
   target_tree->set_source_frame_number(source_frame_number());
   target_tree->set_background_color(background_color());
   target_tree->set_has_transparent_background(has_transparent_background());
 
   if (ContentsTexturesPurged())
     target_tree->SetContentsTexturesPurged();
   else
     target_tree->ResetContentsTexturesPurged();
@@ skipping 91 matching lines @@
   gfx::Vector2dF max_scroll = gfx::Rect(ScrollableSize()).bottom_right() -
       gfx::RectF(ScrollableViewportSize()).bottom_right();
 
   // The viewport may be larger than the contents in some cases, such as
   // having a vertical scrollbar but no horizontal overflow.
   max_scroll.SetToMax(gfx::Vector2dF());
 
   root_scroll_layer_->SetMaxScrollOffset(gfx::ToFlooredVector2d(max_scroll));
 }
 
+void LayerTreeImpl::SetPinchViewportLayerIds(
+    int page_scale_layer_id,
+    int inner_viewport_scroll_layer_id,
+    int outer_viewport_scroll_layer_id) {
+  page_scale_layer_ = FindPendingTreeLayerById(page_scale_layer_id);
+  inner_viewport_scroll_layer_ =
+      FindPendingTreeLayerById(inner_viewport_scroll_layer_id);
+  outer_viewport_scroll_layer_ =
+      FindPendingTreeLayerById(outer_viewport_scroll_layer_id);
+}
+
 void LayerTreeImpl::UpdateSolidColorScrollbars() {
   DCHECK(settings().solid_color_scrollbars);
 
   LayerImpl* root_scroll = RootScrollLayer();
   DCHECK(root_scroll);
   DCHECK(IsActiveTree());
 
   gfx::RectF scrollable_viewport(
       gfx::PointAtOffsetFromOrigin(root_scroll->TotalScrollOffset()),
       ScrollableViewportSize());
@@ skipping 38 matching lines @@
       return;
 
   if (!root_layer())
     return;
 
   {
     TRACE_EVENT1("cc",
                  "LayerTreeImpl::UpdateDrawProperties",
                  "IsActive",
                  IsActiveTree());
+
     LayerTreeHostCommon::CalculateDrawProperties(
         root_layer(),
         layer_tree_host_impl_->DeviceViewport().size(),
         layer_tree_host_impl_->DeviceTransform(),
         device_scale_factor(),
         total_page_scale_factor(),
-        root_scroll_layer_,
+        page_scale_layer_ ? page_scale_layer_ : root_scroll_layer_,
         MaxTextureSize(),
         settings().can_use_lcd_text,
         settings().layer_transforms_should_scale_layer_contents,
         &render_surface_layer_list_);
   }
 
   DCHECK(!needs_update_draw_properties_) <<
       "CalcDrawProperties should not set_needs_update_draw_properties()";
 }
 
@@ skipping 271 matching lines @@
 
 void LayerTreeImpl::ClearLatencyInfo() {
   latency_info_.Clear();
 }
 
 void LayerTreeImpl::WillModifyTilePriorities() {
   layer_tree_host_impl_->SetNeedsManageTiles();
 }
 
 }  // namespace cc