skia: Added chrome implementation of SkDiscardableMemory.

skia/ext/SkDiscardableMemory_chrome.h

+// Copyright (c) 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 SKIA_EXT_SK_DISCARDABLE_MEMORY_CHROME_H_
+#define SKIA_EXT_SK_DISCARDABLE_MEMORY_CHROME_H_
+
+#include "base/memory/discardable_memory.h"
+#include "base/memory/scoped_ptr.h"
+#include "third_party/skia/src/core/SkDiscardableMemory.h"
+
+// This class implements the SkDiscardableMemory interface using
+// base::DiscardableMemory.
+class SK_API SkDiscardableMemoryChrome : public SkDiscardableMemory {
+public:
+  SkDiscardableMemoryChrome();
+  virtual ~SkDiscardableMemoryChrome();
+
+  // Initialize the SkDiscardableMemoryChrome object and lock the memory.
+  // Returns true on success. No memory is allocated if this call returns
+  // false. This call should only be called once.
+  bool InitializeAndLock(size_t bytes);
+
+  // Implementation of SkDiscardableMemory interface.
+  virtual bool lock() OVERRIDE;
+  virtual void* data() OVERRIDE;
+  virtual void unlock() OVERRIDE;
+
+private:
+  scoped_ptr<base::DiscardableMemory> discardable_;
+};
+
+#endif  // SKIA_EXT_SK_DISCARDABLE_MEMORY_CHROME_H_