Dirty rects always contain full tiles with delegated rendering.

cc/test/fake_content_layer.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/test/fake_content_layer.h"
 
+#include "cc/resources/content_layer_updater.h"
 #include "cc/resources/prioritized_resource.h"
 #include "cc/test/fake_content_layer_impl.h"
 
 namespace cc {
 
+class FakeContentLayerUpdater : public ContentLayerUpdater {
+ public:
+  ~FakeContentLayerUpdater() {}

[danakj, 2013/12/04 16:32:17]

It should be virtual, then LGTM

+  using ContentLayerUpdater::content_rect;
+};
+
 FakeContentLayer::FakeContentLayer(ContentLayerClient* client)
     : ContentLayer(client),
       update_count_(0),
       push_properties_count_(0),
       output_surface_created_count_(0),
       always_update_resources_(false) {
   SetAnchorPoint(gfx::PointF(0.f, 0.f));
   SetBounds(gfx::Size(1, 1));
   SetIsDrawable(true);
 }
 
 FakeContentLayer::~FakeContentLayer() {}
 
 scoped_ptr<LayerImpl> FakeContentLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return FakeContentLayerImpl::Create(tree_impl, layer_id_).PassAs<LayerImpl>();
 }
 
 bool FakeContentLayer::Update(ResourceUpdateQueue* queue,
                               const OcclusionTracker* occlusion) {
   bool updated = ContentLayer::Update(queue, occlusion);
   update_count_++;
   return updated || always_update_resources_;
 }
 
+gfx::Rect FakeContentLayer::LastPaintRect() const {
+  return (static_cast<FakeContentLayerUpdater*>
+          (Updater()))->content_rect();
+}
+
 void FakeContentLayer::PushPropertiesTo(LayerImpl* layer) {
   ContentLayer::PushPropertiesTo(layer);
   push_properties_count_++;
 }
 
 void FakeContentLayer::OnOutputSurfaceCreated() {
   ContentLayer::OnOutputSurfaceCreated();
   output_surface_created_count_++;
 }
 
 bool FakeContentLayer::HaveBackingAt(int i, int j) {
   const PrioritizedResource* resource = ResourceAtForTesting(i, j);
   return resource && resource->have_backing_texture();
 }
 
 }  // namespace cc