Replacing SurfaceReferenceBase and SequenceSurfaceReference with Closures

cc/layers/surface_layer.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/layers/surface_layer.h"
 
 #include <stdint.h>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/layers/surface_layer_impl.h"
 #include "cc/output/swap_promise.h"
 #include "cc/surfaces/surface_sequence_generator.h"
 #include "cc/trees/layer_tree_host.h"
 #include "cc/trees/swap_promise_manager.h"
+#include "cc/trees/task_runner_provider.h"
 
 namespace cc {
 
 class SatisfySwapPromise : public SwapPromise {
  public:
   SatisfySwapPromise(
-      std::unique_ptr<SurfaceReferenceBase> surface_ref,
+      base::Closure reference_returner,
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner)
-      : surface_ref_(std::move(surface_ref)),
+      : reference_returner_(reference_returner),
         main_task_runner_(std::move(main_task_runner)) {}
 
   ~SatisfySwapPromise() override {}
 
  private:
   void DidActivate() override {}
 
   void WillSwap(CompositorFrameMetadata* metadata) override {}
 
   void DidSwap() override {
-    main_task_runner_->DeleteSoon(FROM_HERE, surface_ref_.release());
+    main_task_runner_->PostTask(FROM_HERE, reference_returner_);
   }
 
   DidNotSwapAction DidNotSwap(DidNotSwapReason reason) override {
-    main_task_runner_->DeleteSoon(FROM_HERE, surface_ref_.release());
+    main_task_runner_->PostTask(FROM_HERE, reference_returner_);
     return DidNotSwapAction::BREAK_PROMISE;
   }
 
   int64_t TraceId() const override { return 0; }
 
-  std::unique_ptr<SurfaceReferenceBase> surface_ref_;
+  base::Closure reference_returner_;
   scoped_refptr<base::SingleThreadTaskRunner> main_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(SatisfySwapPromise);
 };
 
 scoped_refptr<SurfaceLayer> SurfaceLayer::Create(
     scoped_refptr<SurfaceReferenceFactory> ref_factory) {
   return make_scoped_refptr(new SurfaceLayer(std::move(ref_factory)));
 }
 
 SurfaceLayer::SurfaceLayer(scoped_refptr<SurfaceReferenceFactory> ref_factory)
     : ref_factory_(std::move(ref_factory)) {}
 
 SurfaceLayer::~SurfaceLayer() {
   DCHECK(!layer_tree_host());
 }
 
 void SurfaceLayer::SetSurfaceInfo(const SurfaceInfo& surface_info,
                                   bool stretch_content_to_fill_bounds) {
   RemoveCurrentReference();
   surface_info_ = surface_info;
   if (layer_tree_host()) {
-    current_ref_ =
+    reference_returner_ =
         ref_factory_->CreateReference(layer_tree_host(), surface_info_.id());
   }
   stretch_content_to_fill_bounds_ = stretch_content_to_fill_bounds;
   UpdateDrawsContent(HasDrawableContent());
   SetNeedsPushProperties();
 }
 
 std::unique_ptr<LayerImpl> SurfaceLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return SurfaceLayerImpl::Create(tree_impl, id());
 }
 
 bool SurfaceLayer::HasDrawableContent() const {
   return surface_info_.id().is_valid() && Layer::HasDrawableContent();
 }
 
 void SurfaceLayer::SetLayerTreeHost(LayerTreeHost* host) {
   if (layer_tree_host() == host) {
     Layer::SetLayerTreeHost(host);
     return;
   }
   RemoveCurrentReference();
   Layer::SetLayerTreeHost(host);
   if (layer_tree_host()) {
-    current_ref_ =
+    reference_returner_ =
         ref_factory_->CreateReference(layer_tree_host(), surface_info_.id());
   }
 }
 
 void SurfaceLayer::PushPropertiesTo(LayerImpl* layer) {
   Layer::PushPropertiesTo(layer);
   TRACE_EVENT0("cc", "SurfaceLayer::PushPropertiesTo");
   SurfaceLayerImpl* layer_impl = static_cast<SurfaceLayerImpl*>(layer);
   layer_impl->SetSurfaceInfo(surface_info_);
   layer_impl->SetStretchContentToFillBounds(stretch_content_to_fill_bounds_);
 }
 
 void SurfaceLayer::RemoveCurrentReference() {
-  if (!current_ref_)
+  if (!reference_returner_)
     return;
   auto swap_promise = base::MakeUnique<SatisfySwapPromise>(
-      std::move(current_ref_), base::ThreadTaskRunnerHandle::Get());
+      std::move(reference_returner_),
+      layer_tree_host()->GetTaskRunnerProvider()->MainThreadTaskRunner());

[danakj, 2017/01/11 15:25:28]

One question: If the layer is not in a tree at the time
SetSurfaceInfo/SetLayerTreeHost is called, there's no tree to get a task runner
from. But then also there's no current reference to remove. Should this early
out?

[danakj, 2017/01/11 15:40:38]

Of course, the line below would crash also. I guess there are no users of
SetSurfaceInfo when SurfaceLayer is not in a tree right now. We should add an
early out and unit test this scenario.

This patch LGTM tho.

[Saman Sami, 2017/01/11 16:19:16]

The reference would have never existed if there was no layer tree host. We check
that there actually exists a reference at the very beginning.

   layer_tree_host()->GetSwapPromiseManager()->QueueSwapPromise(
       std::move(swap_promise));
 }
 
 }  // namespace cc