cc: Only allow trees created at the current viewport size to draw.

cc/layer_tree_impl.h

 // 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.
 
 #ifndef CC_LAYER_TREE_IMPL_H_
 #define CC_LAYER_TREE_IMPL_H_
 
 #include "base/hash_tables.h"
 #include "cc/layer_impl.h"
 
@@ skipping 53 matching lines @@
   base::TimeTicks CurrentFrameTime() const;
 
   // Tree specific methods exposed to layer-impl tree.
   // ---------------------------------------------------------------------------
   void SetNeedsRedraw();
 
   // TODO(nduca): These are implemented in cc files temporarily, but will become
   // trivial accessors in a followup patch.
   const LayerTreeDebugState& debug_state() const;
   float device_scale_factor() const;
-  const gfx::Size& device_viewport_size() const;
-  const gfx::Size& layout_viewport_size() const;
   std::string layer_tree_as_text() const;
   DebugRectHistory* debug_rect_history() const;
 
   // Other public methods
   // ---------------------------------------------------------------------------
   LayerImpl* RootLayer() const { return root_layer_.get(); }
   void SetRootLayer(scoped_ptr<LayerImpl>);
   scoped_ptr<LayerImpl> DetachLayerTree();
 
   void pushPropertiesTo(LayerTreeImpl*);
@@ skipping 45 matching lines @@
   }
   float page_scale_factor() const { return page_scale_factor_; }
   float min_page_scale_factor() const { return min_page_scale_factor_; }
   float max_page_scale_factor() const { return max_page_scale_factor_; }
   float page_scale_delta() const  { return page_scale_delta_; }
   void set_sent_page_scale_delta(float delta) {
     sent_page_scale_delta_ = delta;
   }
   float sent_page_scale_delta() const { return sent_page_scale_delta_; }
 
+  void SetViewportSize(gfx::Size layout_viewport_size, gfx::Size device_viewport_size);
+  const gfx::Size& layout_viewport_size() const { return layout_viewport_size_; }
+  const gfx::Size& device_viewport_size() const { return device_viewport_size_; }
+
   // Updates draw properties and render surface layer list
   void UpdateDrawProperties(UpdateDrawPropertiesReason reason);
   void set_needs_update_draw_properties() {
     needs_update_draw_properties_ = true;
   }
   bool needs_update_draw_properties() const {
     return needs_update_draw_properties_;
   }
 
   void set_needs_full_tree_sync(bool needs) { needs_full_tree_sync_ = needs; }
@@ skipping 40 matching lines @@
   LayerImpl* currently_scrolling_layer_;
   SkColor background_color_;
   bool has_transparent_background_;
 
   float page_scale_factor_;
   float page_scale_delta_;
   float sent_page_scale_delta_;
   float min_page_scale_factor_;
   float max_page_scale_factor_;
 
+  gfx::Size device_viewport_size_;
+  gfx::Size layout_viewport_size_;
+
   typedef base::hash_map<int, LayerImpl*> LayerIdMap;
   LayerIdMap layer_id_map_;
 
   // Persisted state for non-impl-side-painting.
   int scrolling_layer_id_from_previous_tree_;
 
   // List of visible layers for the most recently prepared frame. Used for
   // rendering and input event hit testing.
   LayerList render_surface_layer_list_;
 
   bool contents_textures_purged_;
   bool needs_update_draw_properties_;
 
   // In impl-side painting mode, this is true when the tree may contain
   // structural differences relative to the active tree.
   bool needs_full_tree_sync_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeImpl);
 };
 
 }
 
 #endif  // CC_LAYER_TREE_IMPL_H_