Allocate SharedBitmaps on FILE_USER_BLOCKING thread.

content/browser/renderer_host/render_message_filter.h

Index: content/browser/renderer_host/render_message_filter.h
diff --git a/content/browser/renderer_host/render_message_filter.h b/content/browser/renderer_host/render_message_filter.h
index 18f6a2d0d2ee47757446b58e2977b333b1571dab..95a80acbf0c5741a853559753b87241b170b8984 100644
--- a/content/browser/renderer_host/render_message_filter.h
+++ b/content/browser/renderer_host/render_message_filter.h
@@ -209,9 +209,12 @@ class RenderMessageFilter : public BrowserMessageFilter {
   // in the renderer on POSIX due to the sandbox.
   void OnAllocateSharedMemory(uint32 buffer_size,
                               base::SharedMemoryHandle* handle);
+  void AllocateSharedBitmapOnFileThread(uint32 buffer_size,
+                                        const cc::SharedBitmapId& id,
+                                        IPC::Message* reply_msg);
   void OnAllocateSharedBitmap(uint32 buffer_size,
                               const cc::SharedBitmapId& id,
-                              base::SharedMemoryHandle* handle);
+                              IPC::Message* reply_msg);
   void OnAllocatedSharedBitmap(size_t buffer_size,
                                const base::SharedMemoryHandle& handle,
                                const cc::SharedBitmapId& id);