path: root/cc/surfaces/surface_aggregator.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_aggregator.h"

#include <stddef.h>

#include <map>

#include "base/bind.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/stl_util.h"
#include "base/trace_event/trace_event.h"
#include "cc/base/math_util.h"
#include "cc/output/compositor_frame.h"
#include "cc/output/delegated_frame_data.h"
#include "cc/quads/draw_quad.h"
#include "cc/quads/render_pass_draw_quad.h"
#include "cc/quads/shared_quad_state.h"
#include "cc/quads/surface_draw_quad.h"
#include "cc/surfaces/surface.h"
#include "cc/surfaces/surface_factory.h"
#include "cc/surfaces/surface_manager.h"
#include "cc/trees/blocking_task_runner.h"

namespace cc {
namespace {

void MoveMatchingRequests(
    RenderPassId id,
    std::multimap<RenderPassId, scoped_ptr<CopyOutputRequest>>* copy_requests,
    std::vector<scoped_ptr<CopyOutputRequest>>* output_requests) {
  auto request_range = copy_requests->equal_range(id);
  for (auto it = request_range.first; it != request_range.second; ++it) {
    DCHECK(it->second);
    output_requests->push_back(std::move(it->second));
  }
  copy_requests->erase(request_range.first, request_range.second);
}

}  // namespace

SurfaceAggregator::SurfaceAggregator(SurfaceManager* manager,
                                     ResourceProvider* provider,
                                     bool aggregate_only_damaged)
    : manager_(manager),
      provider_(provider),
      next_render_pass_id_(1),
      aggregate_only_damaged_(aggregate_only_damaged),
      weak_factory_(this) {
  DCHECK(manager_);
}

SurfaceAggregator::~SurfaceAggregator() {
  // Notify client of all surfaces being removed.
  contained_surfaces_.clear();
  ProcessAddedAndRemovedSurfaces();
}

SurfaceAggregator::PrewalkResult::PrewalkResult() {}

SurfaceAggregator::PrewalkResult::~PrewalkResult() {}

// Create a clip rect for an aggregated quad from the original clip rect and
// the clip rect from the surface it's on.
SurfaceAggregator::ClipData SurfaceAggregator::CalculateClipRect(
    const ClipData& surface_clip,
    const ClipData& quad_clip,
    const gfx::Transform& target_transform) {
  ClipData out_clip;
  if (surface_clip.is_clipped)
    out_clip = surface_clip;

  if (quad_clip.is_clipped) {
    // TODO(jamesr): This only works if target_transform maps integer
    // rects to integer rects.
    gfx::Rect final_clip =
        MathUtil::MapEnclosingClippedRect(target_transform, quad_clip.rect);
    if (out_clip.is_clipped)
      out_clip.rect.Intersect(final_clip);
    else
      out_clip.rect = final_clip;
    out_clip.is_clipped = true;
  }

  return out_clip;
}

class SurfaceAggregator::RenderPassIdAllocator {
 public:
  explicit RenderPassIdAllocator(int* next_index) : next_index_(next_index) {}
  ~RenderPassIdAllocator() {}

  void AddKnownPass(RenderPassId id) {
    if (id_to_index_map_.find(id) != id_to_index_map_.end())
      return;
    id_to_index_map_[id] = (*next_index_)++;
  }

  RenderPassId Remap(RenderPassId id) {
    DCHECK(id_to_index_map_.find(id) != id_to_index_map_.end());
    return RenderPassId(1, id_to_index_map_[id]);
  }

 private:
  std::unordered_map<RenderPassId, int, RenderPassIdHash> id_to_index_map_;
  int* next_index_;

  DISALLOW_COPY_AND_ASSIGN(RenderPassIdAllocator);
};

static void UnrefHelper(base::WeakPtr<SurfaceFactory> surface_factory,
                        const ReturnedResourceArray& resources,
                        BlockingTaskRunner* main_thread_task_runner) {
  if (surface_factory)
    surface_factory->UnrefResources(resources);
}

RenderPassId SurfaceAggregator::RemapPassId(RenderPassId surface_local_pass_id,
                                            SurfaceId surface_id) {
  scoped_ptr<RenderPassIdAllocator>& allocator =
      render_pass_allocator_map_[surface_id];
  if (!allocator)
    allocator.reset(new RenderPassIdAllocator(&next_render_pass_id_));
  allocator->AddKnownPass(surface_local_pass_id);
  return allocator->Remap(surface_local_pass_id);
}

int SurfaceAggregator::ChildIdForSurface(Surface* surface) {
  SurfaceToResourceChildIdMap::iterator it =
      surface_id_to_resource_child_id_.find(surface->surface_id());
  if (it == surface_id_to_resource_child_id_.end()) {
    int child_id =
        provider_->CreateChild(base::Bind(&UnrefHelper, surface->factory()));
    if (surface->factory()) {
      provider_->SetChildNeedsSyncTokens(
          child_id, surface->factory()->needs_sync_points());
    }
    surface_id_to_resource_child_id_[surface->surface_id()] = child_id;
    return child_id;
  } else {
    return it->second;
  }
}

gfx::Rect SurfaceAggregator::DamageRectForSurface(
    const Surface* surface,
    const RenderPass& source,
    const gfx::Rect& full_rect) const {
  auto it = previous_contained_surfaces_.find(surface->surface_id());
  if (it == previous_contained_surfaces_.end())
    return full_rect;

  int previous_index = it->second;
  if (previous_index == surface->frame_index())
    return gfx::Rect();
  if (previous_index == surface->frame_index() - 1)
    return source.damage_rect;
  return full_rect;
}

void SurfaceAggregator::HandleSurfaceQuad(
    const SurfaceDrawQuad* surface_quad,
    const gfx::Transform& target_transform,
    const ClipData& clip_rect,
    RenderPass* dest_pass) {
  SurfaceId surface_id = surface_quad->surface_id;
  // If this surface's id is already in our referenced set then it creates
  // a cycle in the graph and should be dropped.
  if (referenced_surfaces_.count(surface_id))
    return;
  Surface* surface = manager_->GetSurfaceForId(surface_id);
  if (!surface)
    return;
  const CompositorFrame* frame = surface->GetEligibleFrame();
  if (!frame)
    return;
  const DelegatedFrameData* frame_data = frame->delegated_frame_data.get();
  if (!frame_data)
    return;

  std::multimap<RenderPassId, scoped_ptr<CopyOutputRequest>> copy_requests;
  surface->TakeCopyOutputRequests(&copy_requests);

  const RenderPassList& render_pass_list = frame_data->render_pass_list;
  if (!valid_surfaces_.count(surface->surface_id())) {
    for (auto& request : copy_requests)
      request.second->SendEmptyResult();
    return;
  }

  SurfaceSet::iterator it = referenced_surfaces_.insert(surface_id).first;
  // TODO(vmpstr): provider check is a hack for unittests that don't set up a
  // resource provider.
  ResourceProvider::ResourceIdMap empty_map;
  const ResourceProvider::ResourceIdMap& child_to_parent_map =
      provider_ ? provider_->GetChildToParentMap(ChildIdForSurface(surface))
                : empty_map;
  bool merge_pass =
      surface_quad->shared_quad_state->opacity == 1.f && copy_requests.empty();

  const RenderPassList& referenced_passes = render_pass_list;
  size_t passes_to_copy =
      merge_pass ? referenced_passes.size() - 1 : referenced_passes.size();
  for (size_t j = 0; j < passes_to_copy; ++j) {
    const RenderPass& source = *referenced_passes[j];

    size_t sqs_size = source.shared_quad_state_list.size();
    size_t dq_size = source.quad_list.size();
    scoped_ptr<RenderPass> copy_pass(RenderPass::Create(sqs_size, dq_size));

    RenderPassId remapped_pass_id = RemapPassId(source.id, surface_id);

    copy_pass->SetAll(remapped_pass_id, source.output_rect, gfx::Rect(),
                      source.transform_to_root_target,
                      source.has_transparent_background);

    MoveMatchingRequests(source.id, &copy_requests, &copy_pass->copy_requests);

    // Contributing passes aggregated in to the pass list need to take the
    // transform of the surface quad into account to update their transform to
    // the root surface.
    copy_pass->transform_to_root_target.ConcatTransform(
        surface_quad->shared_quad_state->quad_to_target_transform);
    copy_pass->transform_to_root_target.ConcatTransform(target_transform);
    copy_pass->transform_to_root_target.ConcatTransform(
        dest_pass->transform_to_root_target);

    CopyQuadsToPass(source.quad_list, source.shared_quad_state_list,
                    child_to_parent_map, gfx::Transform(), ClipData(),
                    copy_pass.get(), surface_id);

    dest_pass_list_->push_back(std::move(copy_pass));
  }

  gfx::Transform surface_transform =
      surface_quad->shared_quad_state->quad_to_target_transform;
  surface_transform.ConcatTransform(target_transform);

  const RenderPass& last_pass = *render_pass_list.back();
  if (merge_pass) {
    // TODO(jamesr): Clean up last pass special casing.
    const QuadList& quads = last_pass.quad_list;

    // Intersect the transformed visible rect and the clip rect to create a
    // smaller cliprect for the quad.
    ClipData surface_quad_clip_rect(
        true, MathUtil::MapEnclosingClippedRect(
                  surface_quad->shared_quad_state->quad_to_target_transform,
                  surface_quad->visible_rect));
    if (surface_quad->shared_quad_state->is_clipped) {
      surface_quad_clip_rect.rect.Intersect(
          surface_quad->shared_quad_state->clip_rect);
    }

    ClipData quads_clip =
        CalculateClipRect(clip_rect, surface_quad_clip_rect, target_transform);

    CopyQuadsToPass(quads, last_pass.shared_quad_state_list,
                    child_to_parent_map, surface_transform, quads_clip,
                    dest_pass, surface_id);
  } else {
    RenderPassId remapped_pass_id = RemapPassId(last_pass.id, surface_id);

    SharedQuadState* shared_quad_state =
        CopySharedQuadState(surface_quad->shared_quad_state, target_transform,
                            clip_rect, dest_pass);

    RenderPassDrawQuad* quad =
        dest_pass->CreateAndAppendDrawQuad<RenderPassDrawQuad>();
    quad->SetNew(shared_quad_state,
                 surface_quad->rect,
                 surface_quad->visible_rect,
                 remapped_pass_id,
                 0,
                 gfx::Vector2dF(),
                 gfx::Size(),
                 FilterOperations(),
                 gfx::Vector2dF(),
                 FilterOperations());
  }

  referenced_surfaces_.erase(it);
}

SharedQuadState* SurfaceAggregator::CopySharedQuadState(
    const SharedQuadState* source_sqs,
    const gfx::Transform& target_transform,
    const ClipData& clip_rect,
    RenderPass* dest_render_pass) {
  SharedQuadState* copy_shared_quad_state =
      dest_render_pass->CreateAndAppendSharedQuadState();
  copy_shared_quad_state->CopyFrom(source_sqs);
  // target_transform contains any transformation that may exist
  // between the context that these quads are being copied from (i.e. the
  // surface's draw transform when aggregated from within a surface) to the
  // target space of the pass. This will be identity except when copying the
  // root draw pass from a surface into a pass when the surface draw quad's
  // transform is not identity.
  copy_shared_quad_state->quad_to_target_transform.ConcatTransform(
      target_transform);

  ClipData new_clip_rect = CalculateClipRect(
      clip_rect, ClipData(source_sqs->is_clipped, source_sqs->clip_rect),
      target_transform);
  copy_shared_quad_state->is_clipped = new_clip_rect.is_clipped;
  copy_shared_quad_state->clip_rect = new_clip_rect.rect;
  return copy_shared_quad_state;
}

static gfx::Rect CalculateQuadSpaceDamageRect(
    const gfx::Transform& quad_to_target_transform,
    const gfx::Transform& target_to_root_transform,
    const gfx::Rect& root_damage_rect) {
  gfx::Transform quad_to_root_transform(target_to_root_transform,
                                        quad_to_target_transform);
  gfx::Transform inverse_transform(gfx::Transform::kSkipInitialization);
  bool inverse_valid = quad_to_root_transform.GetInverse(&inverse_transform);
  DCHECK(inverse_valid);

  return MathUtil::ProjectEnclosingClippedRect(inverse_transform,
                                               root_damage_rect);
}

void SurfaceAggregator::CopyQuadsToPass(
    const QuadList& source_quad_list,
    const SharedQuadStateList& source_shared_quad_state_list,
    const ResourceProvider::ResourceIdMap& child_to_parent_map,
    const gfx::Transform& target_transform,
    const ClipData& clip_rect,
    RenderPass* dest_pass,
    SurfaceId surface_id) {
  const SharedQuadState* last_copied_source_shared_quad_state = nullptr;
  const SharedQuadState* dest_shared_quad_state = nullptr;
  // If the current frame has copy requests then aggregate the entire
  // thing, as otherwise parts of the copy requests may be ignored.
  const bool ignore_undamaged = aggregate_only_damaged_ && !has_copy_requests_;
  // Damage rect in the quad space of the current shared quad state.
  // TODO(jbauman): This rect may contain unnecessary area if
  // transform isn't axis-aligned.
  gfx::Rect damage_rect_in_quad_space;

#if DCHECK_IS_ON()
  // If quads have come in with SharedQuadState out of order, or when quads have
  // invalid SharedQuadState pointer, it should DCHECK.
  SharedQuadStateList::ConstIterator sqs_iter =
      source_shared_quad_state_list.begin();
  for (const auto& quad : source_quad_list) {
    while (sqs_iter != source_shared_quad_state_list.end() &&
           quad->shared_quad_state != *sqs_iter) {
      ++sqs_iter;
    }
    DCHECK(sqs_iter != source_shared_quad_state_list.end());
  }
#endif

  for (const auto& quad : source_quad_list) {
    if (quad->material == DrawQuad::SURFACE_CONTENT) {
      const SurfaceDrawQuad* surface_quad = SurfaceDrawQuad::MaterialCast(quad);
      // HandleSurfaceQuad may add other shared quad state, so reset the
      // current data.
      last_copied_source_shared_quad_state = nullptr;

      if (ignore_undamaged) {
        gfx::Transform quad_to_target_transform(
            target_transform,
            quad->shared_quad_state->quad_to_target_transform);
        damage_rect_in_quad_space = CalculateQuadSpaceDamageRect(
            quad_to_target_transform, dest_pass->transform_to_root_target,
            root_damage_rect_);
        if (!damage_rect_in_quad_space.Intersects(quad->visible_rect))
          continue;
      }
      HandleSurfaceQuad(surface_quad, target_transform, clip_rect, dest_pass);
    } else {
      if (quad->shared_quad_state != last_copied_source_shared_quad_state) {
        dest_shared_quad_state = CopySharedQuadState(
            quad->shared_quad_state, target_transform, clip_rect, dest_pass);
        last_copied_source_shared_quad_state = quad->shared_quad_state;
        if (aggregate_only_damaged_ && !has_copy_requests_) {
          damage_rect_in_quad_space = CalculateQuadSpaceDamageRect(
              dest_shared_quad_state->quad_to_target_transform,
              dest_pass->transform_to_root_target, root_damage_rect_);
        }
      }

      if (ignore_undamaged) {
        if (!damage_rect_in_quad_space.Intersects(quad->visible_rect))
          continue;
      }

      DrawQuad* dest_quad;
      if (quad->material == DrawQuad::RENDER_PASS) {
        const RenderPassDrawQuad* pass_quad =
            RenderPassDrawQuad::MaterialCast(quad);
        RenderPassId original_pass_id = pass_quad->render_pass_id;
        RenderPassId remapped_pass_id =
            RemapPassId(original_pass_id, surface_id);

        dest_quad = dest_pass->CopyFromAndAppendRenderPassDrawQuad(
            pass_quad, dest_shared_quad_state, remapped_pass_id);
      } else {
        dest_quad =
            dest_pass->CopyFromAndAppendDrawQuad(quad, dest_shared_quad_state);
      }
      if (!child_to_parent_map.empty()) {
        for (ResourceId& resource_id : dest_quad->resources) {
          ResourceProvider::ResourceIdMap::const_iterator it =
              child_to_parent_map.find(resource_id);
          DCHECK(it != child_to_parent_map.end());

          DCHECK_EQ(it->first, resource_id);
          ResourceId remapped_id = it->second;
          resource_id = remapped_id;
        }
      }
    }
  }
}

void SurfaceAggregator::CopyPasses(const DelegatedFrameData* frame_data,
                                   Surface* surface) {
  // The root surface is allowed to have copy output requests, so grab them
  // off its render passes.
  std::multimap<RenderPassId, scoped_ptr<CopyOutputRequest>> copy_requests;
  surface->TakeCopyOutputRequests(&copy_requests);

  const RenderPassList& source_pass_list = frame_data->render_pass_list;
  DCHECK(valid_surfaces_.count(surface->surface_id()));
  if (!valid_surfaces_.count(surface->surface_id()))
    return;

  // TODO(vmpstr): provider check is a hack for unittests that don't set up a
  // resource provider.
  ResourceProvider::ResourceIdMap empty_map;
  const ResourceProvider::ResourceIdMap& child_to_parent_map =
      provider_ ? provider_->GetChildToParentMap(ChildIdForSurface(surface))
                : empty_map;
  for (size_t i = 0; i < source_pass_list.size(); ++i) {
    const RenderPass& source = *source_pass_list[i];

    size_t sqs_size = source.shared_quad_state_list.size();
    size_t dq_size = source.quad_list.size();
    scoped_ptr<RenderPass> copy_pass(RenderPass::Create(sqs_size, dq_size));

    MoveMatchingRequests(source.id, &copy_requests, &copy_pass->copy_requests);

    RenderPassId remapped_pass_id =
        RemapPassId(source.id, surface->surface_id());

    copy_pass->SetAll(remapped_pass_id, source.output_rect, gfx::Rect(),
                      source.transform_to_root_target,
                      source.has_transparent_background);

    CopyQuadsToPass(source.quad_list, source.shared_quad_state_list,
                    child_to_parent_map, gfx::Transform(), ClipData(),
                    copy_pass.get(), surface->surface_id());

    dest_pass_list_->push_back(std::move(copy_pass));
  }
}

void SurfaceAggregator::ProcessAddedAndRemovedSurfaces() {
  for (const auto& surface : previous_contained_surfaces_) {
    if (!contained_surfaces_.count(surface.first)) {
      // Release resources of removed surface.
      SurfaceToResourceChildIdMap::iterator it =
          surface_id_to_resource_child_id_.find(surface.first);
      if (it != surface_id_to_resource_child_id_.end()) {
        provider_->DestroyChild(it->second);
        surface_id_to_resource_child_id_.erase(it);
      }

      // Notify client of removed surface.
      Surface* surface_ptr = manager_->GetSurfaceForId(surface.first);
      if (surface_ptr) {
        surface_ptr->RunDrawCallbacks(SurfaceDrawStatus::DRAW_SKIPPED);
      }
    }
  }
}

// Walk the Surface tree from surface_id. Validate the resources of the current
// surface and its descendants, check if there are any copy requests, and
// return the combined damage rect.
gfx::Rect SurfaceAggregator::PrewalkTree(SurfaceId surface_id,
                                         PrewalkResult* result) {
  // This is for debugging a possible use after free.
  // TODO(jbauman): Remove this once we have enough information.
  // http://crbug.com/560181
  base::WeakPtr<SurfaceAggregator> debug_weak_this = weak_factory_.GetWeakPtr();

  if (referenced_surfaces_.count(surface_id))
    return gfx::Rect();
  Surface* surface = manager_->GetSurfaceForId(surface_id);
  if (!surface) {
    contained_surfaces_[surface_id] = 0;
    return gfx::Rect();
  }
  contained_surfaces_[surface_id] = surface->frame_index();
  const CompositorFrame* surface_frame = surface->GetEligibleFrame();
  if (!surface_frame)
    return gfx::Rect();
  const DelegatedFrameData* frame_data =
      surface_frame->delegated_frame_data.get();
  if (!frame_data)
    return gfx::Rect();
  int child_id = 0;
  // TODO(jbauman): hack for unit tests that don't set up rp
  if (provider_) {
    child_id = ChildIdForSurface(surface);
    if (surface->factory())
      surface->factory()->RefResources(frame_data->resource_list);
    provider_->ReceiveFromChild(child_id, frame_data->resource_list);
  }
  CHECK(debug_weak_this.get());

  ResourceProvider::ResourceIdSet referenced_resources;
  size_t reserve_size = frame_data->resource_list.size();
  referenced_resources.reserve(reserve_size);

  bool invalid_frame = false;
  ResourceProvider::ResourceIdMap empty_map;
  const ResourceProvider::ResourceIdMap& child_to_parent_map =
      provider_ ? provider_->GetChildToParentMap(child_id) : empty_map;

  CHECK(debug_weak_this.get());
  // Each pair in the vector is a child surface and the transform from its
  // target to the root target of this surface.
  std::vector<std::pair<SurfaceId, gfx::Transform>> child_surfaces;
  for (const auto& render_pass : frame_data->render_pass_list) {
    for (const auto& quad : render_pass->quad_list) {
      if (quad->material == DrawQuad::SURFACE_CONTENT) {
        const SurfaceDrawQuad* surface_quad =
            SurfaceDrawQuad::MaterialCast(quad);
        gfx::Transform target_to_surface_transform(
            render_pass->transform_to_root_target,
            surface_quad->shared_quad_state->quad_to_target_transform);
        child_surfaces.push_back(std::make_pair(surface_quad->surface_id,
                                                target_to_surface_transform));
      }

      if (!provider_)
        continue;
      for (ResourceId resource_id : quad->resources) {
        if (!child_to_parent_map.count(resource_id)) {
          invalid_frame = true;
          break;
        }
        referenced_resources.insert(resource_id);
      }
    }
  }

  if (invalid_frame)
    return gfx::Rect();
  CHECK(debug_weak_this.get());
  valid_surfaces_.insert(surface->surface_id());

  if (provider_)
    provider_->DeclareUsedResourcesFromChild(child_id, referenced_resources);
  CHECK(debug_weak_this.get());

  gfx::Rect damage_rect;
  if (!frame_data->render_pass_list.empty()) {
    RenderPass* last_pass = frame_data->render_pass_list.back().get();
    damage_rect =
        DamageRectForSurface(surface, *last_pass, last_pass->output_rect);
  }

  // Avoid infinite recursion by adding current surface to
  // referenced_surfaces_.
  SurfaceSet::iterator it =
      referenced_surfaces_.insert(surface->surface_id()).first;
  for (const auto& surface_info : child_surfaces) {
    gfx::Rect surface_damage = PrewalkTree(surface_info.first, result);
    damage_rect.Union(
        MathUtil::MapEnclosingClippedRect(surface_info.second, surface_damage));
  }

  CHECK(debug_weak_this.get());
  for (const auto& surface_id : surface_frame->metadata.referenced_surfaces) {
    if (!contained_surfaces_.count(surface_id)) {
      result->undrawn_surfaces.insert(surface_id);
      PrewalkTree(surface_id, result);
    }
  }

  CHECK(debug_weak_this.get());
  if (surface->factory())
    surface->factory()->WillDrawSurface(surface->surface_id(), damage_rect);

  CHECK(debug_weak_this.get());
  for (const auto& render_pass : frame_data->render_pass_list)
    result->has_copy_requests |= !render_pass->copy_requests.empty();

  referenced_surfaces_.erase(it);
  return damage_rect;
}

void SurfaceAggregator::CopyUndrawnSurfaces(PrewalkResult* prewalk_result) {
  // undrawn_surfaces are Surfaces that were identified by prewalk as being
  // referenced by a drawn Surface, but aren't contained in a SurfaceDrawQuad.
  // They need to be iterated over to ensure that any copy requests on them
  // (or on Surfaces they reference) are executed.
  std::vector<SurfaceId> surfaces_to_copy(
      prewalk_result->undrawn_surfaces.begin(),
      prewalk_result->undrawn_surfaces.end());

  for (size_t i = 0; i < surfaces_to_copy.size(); i++) {
    SurfaceId surface_id = surfaces_to_copy[i];
    Surface* surface = manager_->GetSurfaceForId(surface_id);
    if (!surface)
      continue;
    const CompositorFrame* surface_frame = surface->GetEligibleFrame();
    if (!surface_frame)
      continue;
    bool surface_has_copy_requests = false;
    for (const auto& render_pass :
         surface_frame->delegated_frame_data->render_pass_list) {
      surface_has_copy_requests |= !render_pass->copy_requests.empty();
    }
    if (!surface_has_copy_requests) {
      // Children are not necessarily included in undrawn_surfaces (because
      // they weren't referenced directly from a drawn surface), but may have
      // copy requests, so make sure to check them as well.
      for (const auto& child_id : surface_frame->metadata.referenced_surfaces) {
        // Don't iterate over the child Surface if it was already listed as a
        // child of a different Surface, or in the case where there's infinite
        // recursion.
        if (!prewalk_result->undrawn_surfaces.count(child_id)) {
          surfaces_to_copy.push_back(child_id);
          prewalk_result->undrawn_surfaces.insert(child_id);
        }
      }
    } else {
      SurfaceSet::iterator it = referenced_surfaces_.insert(surface_id).first;
      CopyPasses(surface_frame->delegated_frame_data.get(), surface);
      referenced_surfaces_.erase(it);
    }
  }
}

scoped_ptr<CompositorFrame> SurfaceAggregator::Aggregate(SurfaceId surface_id) {
  Surface* surface = manager_->GetSurfaceForId(surface_id);
  DCHECK(surface);
  contained_surfaces_[surface_id] = surface->frame_index();
  const CompositorFrame* root_surface_frame = surface->GetEligibleFrame();
  if (!root_surface_frame)
    return nullptr;
  TRACE_EVENT0("cc", "SurfaceAggregator::Aggregate");

  scoped_ptr<CompositorFrame> frame(new CompositorFrame);
  frame->delegated_frame_data = make_scoped_ptr(new DelegatedFrameData);

  DCHECK(root_surface_frame->delegated_frame_data);

  dest_resource_list_ = &frame->delegated_frame_data->resource_list;
  dest_pass_list_ = &frame->delegated_frame_data->render_pass_list;

  valid_surfaces_.clear();
  PrewalkResult prewalk_result;
  root_damage_rect_ = PrewalkTree(surface_id, &prewalk_result);
  has_copy_requests_ = prewalk_result.has_copy_requests;

  CopyUndrawnSurfaces(&prewalk_result);
  SurfaceSet::iterator it = referenced_surfaces_.insert(surface_id).first;
  CopyPasses(root_surface_frame->delegated_frame_data.get(), surface);
  referenced_surfaces_.erase(it);

  DCHECK(referenced_surfaces_.empty());

  if (dest_pass_list_->empty())
    return nullptr;
  dest_pass_list_->back()->damage_rect = root_damage_rect_;

  dest_pass_list_ = NULL;
  ProcessAddedAndRemovedSurfaces();
  contained_surfaces_.swap(previous_contained_surfaces_);
  contained_surfaces_.clear();

  for (SurfaceIndexMap::iterator it = previous_contained_surfaces_.begin();
       it != previous_contained_surfaces_.end();
       ++it) {
    Surface* surface = manager_->GetSurfaceForId(it->first);
    if (surface)
      surface->TakeLatencyInfo(&frame->metadata.latency_info);
  }

  // TODO(jamesr): Aggregate all resource references into the returned frame's
  // resource list.

  return frame;
}

void SurfaceAggregator::ReleaseResources(SurfaceId surface_id) {
  SurfaceToResourceChildIdMap::iterator it =
      surface_id_to_resource_child_id_.find(surface_id);
  if (it != surface_id_to_resource_child_id_.end()) {
    provider_->DestroyChild(it->second);
    surface_id_to_resource_child_id_.erase(it);
  }
}

void SurfaceAggregator::SetFullDamageForSurface(SurfaceId surface_id) {
  auto it = previous_contained_surfaces_.find(surface_id);
  if (it == previous_contained_surfaces_.end())
    return;
  // Set the last drawn index as 0 to ensure full damage next time it's drawn.
  it->second = 0;
}

}  // namespace cc