android: Migrate old content readback to use async readback (and delegated renderer)

content/browser/android/transient_ui_resource.h

+// 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 CONTENT_BROWSER_ANDROID_TRANSIENT_UI_RESOURCE_H_
+#define CONTENT_BROWSER_ANDROID_TRANSIENT_UI_RESOURCE_H_
+
+#include "base/memory/ref_counted.h"
+#include "cc/resources/ui_resource_client.h"
+#include "ui/gfx/size.h"
+
+namespace cc {
+
+class LayerTreeHost;
+class UIResourceBitmap;
+
+}
+
+namespace content {
+
+// This UIResourceClient immediately frees the pixels after it has been queried
+// once.  Subsequent GetBitmap() calls will return a small holder.

[no sievers, 2014/01/28 20:47:22]

Do we really need this class? The way this works, can't the Compositor just
implement GetBitmap()?

Then we don't have to pass around the weak pointers and such, and the lifetime
oh objects is better defined.

[powei, 2014/01/29 13:53:17]

Done.

+class TransientUIResource : public cc::UIResourceClient {
+ public:
+  static scoped_ptr<TransientUIResource> Create(
+      cc::LayerTreeHost* host,
+      const cc::UIResourceBitmap& bitmap);
+  virtual ~TransientUIResource();
+
+  // UIResourceClient implementation.
+  virtual cc::UIResourceBitmap GetBitmap(cc::UIResourceId uid,
+                                         bool resource_lost) OVERRIDE;
+  cc::UIResourceId id() { return id_; }
+
+ protected:
+  TransientUIResource(cc::LayerTreeHost* host,
+                      const cc::UIResourceBitmap& bitmap);
+
+  scoped_ptr<cc::UIResourceBitmap> bitmap_;
+  cc::LayerTreeHost* host_;
+  cc::UIResourceId id_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TransientUIResource);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ANDROID_TRANSIENT_UI_RESOURCE_H_