Don't overwrit image data case entries that are just marked usable.

ppapi/proxy/ppb_image_data_proxy.h

 // Copyright (c) 2012 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 PPAPI_PPB_IMAGE_DATA_PROXY_H_
 #define PPAPI_PPB_IMAGE_DATA_PROXY_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
 #include "build/build_config.h"
@@ skipping 44 matching lines @@
   // PPB_ImageData API.
   virtual PP_Bool Describe(PP_ImageDataDesc* desc) OVERRIDE;
   virtual void* Map() OVERRIDE;
   virtual void Unmap() OVERRIDE;
   virtual int32_t GetSharedMemory(int* handle, uint32_t* byte_count) OVERRIDE;
   virtual skia::PlatformCanvas* GetPlatformCanvas() OVERRIDE;
   virtual SkCanvas* GetCanvas() OVERRIDE;
 
   const PP_ImageDataDesc& desc() const { return desc_; }
 
-  // Fills the contents of the image with 0.
-  void ZeroContents();
+  void set_used_in_replace_contents() { used_in_replace_contents_ = true; }
+
+  // Prepares this image data to be recycled to the plugin. The contents will be
+  // cleared if zero_contents is set.
+  void RecycleToPlugin(bool zero_contents);
 
 #if !defined(OS_NACL)
   static ImageHandle NullHandle();
   static ImageHandle HandleFromInt(int32_t i);
 #endif
 
  private:
   PP_ImageDataDesc desc_;
 
 #if defined(OS_NACL)
   base::SharedMemory shm_;
   uint32 size_;
   int map_count_;
 #else
   scoped_ptr<TransportDIB> transport_dib_;
 
   // Null when the image isn't mapped.
   scoped_ptr<skia::PlatformCanvas> mapped_canvas_;
 #endif
 
+  // Set to true when this ImageData has been used in a call to
+  // Graphics2D.ReplaceContents. This is used to signal that it can be cached.
+  bool used_in_replace_contents_;
+
   DISALLOW_COPY_AND_ASSIGN(ImageData);
 };
 
 class PPB_ImageData_Proxy : public InterfaceProxy {
  public:
   PPB_ImageData_Proxy(Dispatcher* dispatcher);
   virtual ~PPB_ImageData_Proxy();
 
   static PP_Resource CreateProxyResource(PP_Instance instance,
                                          PP_ImageDataFormat format,
@@ skipping 25 matching lines @@
   // Host->Plugin message handlers.
   void OnPluginMsgNotifyUnusedImageData(const HostResource& old_image_data);
 
   DISALLOW_COPY_AND_ASSIGN(PPB_ImageData_Proxy);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PPB_IMAGE_DATA_PROXY_H_