Android should be able to discard CachedResources

Source/core/platform/PurgeableBuffer.h

 /*
  * Copyright (C) 2008, 2010 Apple Inc. All Rights Reserved.
+ * Copyright (C) 2013 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
  */
 
 #ifndef PurgeableBuffer_h
 #define PurgeableBuffer_h
 
-#include "core/platform/PurgePriority.h"
-#include <wtf/PassOwnPtr.h>
-#include <wtf/Vector.h>
+#include "wtf/OwnPtr.h"
+#include "wtf/PassOwnPtr.h"
+
+namespace WebKit {
+class WebDiscardableMemory;
+}
 
 namespace WebCore {
 
-    class PurgeableBuffer {
-        WTF_MAKE_NONCOPYABLE(PurgeableBuffer);
-    public:
-        static PassOwnPtr<PurgeableBuffer> create(const char* data, size_t);
-        
-        ~PurgeableBuffer();
+class PurgeableBuffer {
+    WTF_MAKE_NONCOPYABLE(PurgeableBuffer);
+public:
+    static PassOwnPtr<PurgeableBuffer> create(const char* data, size_t);
+    ~PurgeableBuffer();
 
-        // Call makePurgeable(false) and check the return value before accessing the data.
-        const char* data() const;
-        size_t size() const { return m_size; }
-        
-        PurgePriority purgePriority() const { return m_purgePriority; }
-        void setPurgePriority(PurgePriority priority) { m_purgePriority = priority; }
-        
-        bool isPurgeable() const { return m_state != NonVolatile; }
-        bool wasPurged() const;
+    // Call lock and check the return value before accessing the data.
+    const char* data() const;
+    size_t size() const { return m_size; }
 
-        bool makePurgeable(bool purgeable);
+    bool isPurgeable() const { return m_state != Locked; }
+    bool wasPurged() const;
 
-    private:
-        PurgeableBuffer(char* data, size_t);
-    
-        char* m_data;
-        size_t m_size;
-        PurgePriority m_purgePriority;
+    bool lock();
+    void unlock();
 
-        enum State { NonVolatile, Volatile, Purged };
-        mutable State m_state;
+private:
+    enum State {
+        Locked,
+        Unlocked,
+        Purged
     };
 
-#if !ENABLE(PURGEABLE_MEMORY)
-    inline PassOwnPtr<PurgeableBuffer> PurgeableBuffer::create(const char*, size_t) { return nullptr; }
-    inline PurgeableBuffer::~PurgeableBuffer() { }
-    inline const char* PurgeableBuffer::data() const { return 0; }
-    inline bool PurgeableBuffer::wasPurged() const { return false; }
-    inline bool PurgeableBuffer::makePurgeable(bool) { return false; }
-#endif
-    
+    PurgeableBuffer(PassOwnPtr<WebKit::WebDiscardableMemory>, const char* data, size_t);
+
+    OwnPtr<WebKit::WebDiscardableMemory> m_memory;
+    size_t m_size;
+    State m_state;
+};
+
 }
 
 #endif