Dirty rects always contain full tiles with delegated rendering.

cc/test/fake_content_layer.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_TEST_FAKE_CONTENT_LAYER_H_
 #define CC_TEST_FAKE_CONTENT_LAYER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/layers/content_layer.h"
 
@@ skipping 11 matching lines @@
   size_t update_count() const { return update_count_; }
   void reset_update_count() { update_count_ = 0; }
 
   size_t push_properties_count() const { return push_properties_count_; }
   void reset_push_properties_count() { push_properties_count_ = 0; }
 
   virtual bool Update(
       ResourceUpdateQueue* queue,
       const OcclusionTracker* occlusion) OVERRIDE;
 
+  gfx::Rect LastPaintRect() const;
+
   void set_always_update_resources(bool always_update_resources) {
     always_update_resources_ = always_update_resources;
   }
 
   virtual void PushPropertiesTo(LayerImpl* layer) OVERRIDE;
 
   virtual void OnOutputSurfaceCreated() OVERRIDE;
   size_t output_surface_created_count() const {
     return output_surface_created_count_;
   }
 
   bool HaveBackingAt(int i, int j);
 
  private:
   explicit FakeContentLayer(ContentLayerClient* client);
   virtual ~FakeContentLayer();
 
   size_t update_count_;
   size_t push_properties_count_;
   size_t output_surface_created_count_;
   bool always_update_resources_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_CONTENT_LAYER_H_