Aggregate damage rects in surface aggregator

cc/surfaces/surface.cc

 // Copyright 2014 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/surfaces/surface.h"
 
 #include "cc/output/compositor_frame.h"
 #include "cc/surfaces/surface_factory.h"
 
 namespace cc {
 
+// The frame index starts at 2 so that empty frames will be treated as
+// completely damaged the first time they're drawn from.
+static const int kFrameIndexStart = 2;
+
 Surface::Surface(SurfaceId id, const gfx::Size& size, SurfaceFactory* factory)
-    : surface_id_(id), size_(size), factory_(factory) {
+    : surface_id_(id),
+      size_(size),
+      factory_(factory),
+      frame_index_(kFrameIndexStart) {
 }
 
 Surface::~Surface() {
   if (current_frame_) {
     ReturnedResourceArray current_resources;
     TransferableResource::ReturnResources(
         current_frame_->delegated_frame_data->resource_list,
         &current_resources);
     factory_->UnrefResources(current_resources);
   }
 }
 
 void Surface::QueueFrame(scoped_ptr<CompositorFrame> frame,
                          const base::Closure& callback) {
   scoped_ptr<CompositorFrame> previous_frame = current_frame_.Pass();
   current_frame_ = frame.Pass();
   factory_->ReceiveFromChild(
       current_frame_->delegated_frame_data->resource_list);
+  ++frame_index_;
 
   if (previous_frame) {
     ReturnedResourceArray previous_resources;
     TransferableResource::ReturnResources(
         previous_frame->delegated_frame_data->resource_list,
         &previous_resources);
     factory_->UnrefResources(previous_resources);
   }
   if (!draw_callback_.is_null())
     draw_callback_.Run();
   draw_callback_ = callback;
 }
 
 const CompositorFrame* Surface::GetEligibleFrame() {
   return current_frame_.get();
 }
 
 void Surface::RunDrawCallbacks() {
   if (!draw_callback_.is_null()) {
     base::Closure callback = draw_callback_;
     draw_callback_ = base::Closure();
     callback.Run();
   }
 }
 
 }  // namespace cc