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

cc/layers/delegated_frame_provider.h

Index: cc/layers/delegated_frame_provider.h
diff --git a/cc/layers/delegated_frame_provider.h b/cc/layers/delegated_frame_provider.h
new file mode 100644
index 0000000000000000000000000000000000000000..b71c74881b280d5d8933f403839a349abd008d16
--- /dev/null
+++ b/cc/layers/delegated_frame_provider.h
@@ -0,0 +1,75 @@
+// 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_PROVIDER_H_
+#define CC_LAYERS_DELEGATED_FRAME_PROVIDER_H_
+
+#include <vector>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "cc/base/cc_export.h"
+#include "cc/resources/return_callback.h"
+#include "cc/resources/returned_resource.h"
+#include "ui/gfx/rect_f.h"
+#include "ui/gfx/size.h"
+
+namespace cc {
+class DelegatedFrameData;
+class DelegatedFrameResourceCollection;
+class DelegatedRendererLayer;
+
+// Only one observing layer has ownership of the DelegatedFrameProvider. Only
+// the active observer should call GetFrameDataAndRefResources(). All frames
+// provided by a single DelegatedFrameProvider must have the same size. A new
+// provider must be used for frames of a different size.
+class CC_EXPORT DelegatedFrameProvider
+    : public base::RefCounted<DelegatedFrameProvider> {
+ public:
+  explicit DelegatedFrameProvider(
+      const scoped_refptr<DelegatedFrameResourceCollection>&
+          resource_collection,
+      scoped_ptr<DelegatedFrameData> frame);
+
+  void AddObserver(DelegatedRendererLayer* layer);
+  void RemoveObserver(DelegatedRendererLayer* layer);
+
+  void SetFrameData(scoped_ptr<DelegatedFrameData> frame);
+
+  // The DelegatedFrameData returned here must be displayed in order to not
+  // lose track of damage.
+  DelegatedFrameData* GetFrameDataAndRefResources(
+      DelegatedRendererLayer* observer,
+      gfx::RectF* damage);
+
+  ReturnCallback GetReturnResourcesCallbackForImplThread();
+  void UnrefResourcesOnMainThread(const ReturnedResourceArray& unused);
+
+  gfx::Size frame_size() const { return frame_size_; }
+
+ private:
+  friend class base::RefCounted<DelegatedFrameProvider>;
+  ~DelegatedFrameProvider();
+
+  scoped_refptr<DelegatedFrameResourceCollection> resource_collection_;
+
+  scoped_ptr<DelegatedFrameData> frame_;
+
+  struct Observer {
+    DelegatedRendererLayer* layer;
+    gfx::RectF damage;
+
+    Observer(DelegatedRendererLayer* layer, const gfx::RectF& damage)
+        : layer(layer), damage(damage) {}
+  };
+  std::vector<Observer> observers_;
+
+  gfx::Size frame_size_;
+
+  DISALLOW_COPY_AND_ASSIGN(DelegatedFrameProvider);
+};
+
+}  // namespace cc
+
+#endif  // CC_LAYERS_DELEGATED_FRAME_PROVIDER_H_