cc: Make LayerTreeTests use a DelegatingRenderer and Display.

cc/surfaces/display.h

Index: cc/surfaces/display.h
diff --git a/cc/surfaces/display.h b/cc/surfaces/display.h
index 24942a92402b606d4fab4f97d6a8f70adf58d99a..0fc2fb0a7484bf5f6a4853c93ef61022cb655521 100644
--- a/cc/surfaces/display.h
+++ b/cc/surfaces/display.h
@@ -115,6 +115,7 @@ class CC_SURFACES_EXPORT Display : public DisplaySchedulerClient,
   }
 
   bool has_scheduler() const { return !!scheduler_; }
+  DirectRenderer* renderer_for_testing() const { return renderer_.get(); }
 
  private:
   void InitializeRenderer();
@@ -124,8 +125,8 @@ class CC_SURFACES_EXPORT Display : public DisplaySchedulerClient,
   gpu::GpuMemoryBufferManager* const gpu_memory_buffer_manager_;
   const RendererSettings settings_;
 
-  DisplayClient* client_;
-  SurfaceManager* surface_manager_;
+  DisplayClient* client_ = nullptr;
+  SurfaceManager* surface_manager_ = nullptr;
   uint32_t compositor_surface_namespace_;
   SurfaceId current_surface_id_;
   gfx::Size current_surface_size_;