aura: Allow delegated frames to be used by more than one impl layer.

cc/layers/delegated_frame_resource_collection.h

Index: cc/layers/delegated_frame_resource_collection.h
diff --git a/cc/layers/delegated_frame_resource_collection.h b/cc/layers/delegated_frame_resource_collection.h
new file mode 100644
index 0000000000000000000000000000000000000000..754d4535ea72303d8b7911802267fea3ee2a89ed
--- /dev/null
+++ b/cc/layers/delegated_frame_resource_collection.h
@@ -0,0 +1,69 @@
+// Copyright 2013 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.
+
+#ifndef CC_LAYERS_DELEGATED_FRAME_RESOURCE_COLLECTION_H_
+#define CC_LAYERS_DELEGATED_FRAME_RESOURCE_COLLECTION_H_
+
+#include "base/containers/hash_tables.h"
+#include "base/memory/ref_counted.h"
+#include "base/threading/thread_checker.h"
+#include "cc/base/cc_export.h"
+#include "cc/resources/return_callback.h"
+#include "cc/resources/returned_resource.h"
+#include "cc/resources/transferable_resource.h"
+
+namespace cc {
+class BlockingTaskRunner;
+
+class CC_EXPORT DelegatedFrameResourceCollectionClient {
+ public:
+  // Called to inform the client that returned resources can be
+  // grabbed off the DelegatedFrameResourceCollection.
+  virtual void UnusedResourcesAreAvailable() = 0;
+};
+
+class CC_EXPORT DelegatedFrameResourceCollection
+    : public base::RefCounted<DelegatedFrameResourceCollection> {
+ public:
+  explicit DelegatedFrameResourceCollection();
+
+  void SetClient(DelegatedFrameResourceCollectionClient* client);
+
+  void TakeUnusedResourcesForChildCompositor(ReturnedResourceArray* array);
+
+  // Methods for DelegatedFrameProvider.
+  void RefResources(const TransferableResourceArray& resources);
+  ReturnCallback GetReturnResourcesCallbackForImplThread();
+  void ReceivedResources(const TransferableResourceArray& resources);
+  void ReturnResources(const ReturnedResourceArray& returned);
+
+ private:
+  friend base::RefCounted<DelegatedFrameResourceCollection>;
+  ~DelegatedFrameResourceCollection();
+
+  void UnrefResources(const ReturnedResourceArray& returned);
+  void UnrefResourcesOnImplThread(
+      scoped_refptr<BlockingTaskRunner> main_thread_runner,
+      const ReturnedResourceArray& returned);
+
+  DelegatedFrameResourceCollectionClient* client_;
+  scoped_refptr<BlockingTaskRunner> main_thread_runner_;
+
+  ReturnedResourceArray returned_resources_for_child_compositor_;
+
+  struct RefCount {
+    int refs_to_return;
+    int refs_to_wait_for;
+  };
+  typedef base::hash_map<unsigned, RefCount> ResourceIdRefCountMap;
+  ResourceIdRefCountMap resource_id_ref_count_map_;
+
+  base::ThreadChecker main_thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(DelegatedFrameResourceCollection);
+};
+
+}  // namespace cc
+
+#endif  // CC_LAYERS_DELEGATED_FRAME_RESOURCE_COLLECTION_H_