Pepper: always delete ResourceMessageFilter objects on the creation thread.

ppapi/host/resource_message_filter.h

Index: ppapi/host/resource_message_filter.h
diff --git a/ppapi/host/resource_message_filter.h b/ppapi/host/resource_message_filter.h
index ef00cf7ae22f7ee33430b9cfa48c46ca7f532591..49d0a6ee64c520515dba4bd2ad1bedb34664f598 100644
--- a/ppapi/host/resource_message_filter.h
+++ b/ppapi/host/resource_message_filter.h
@@ -24,6 +24,15 @@ namespace ppapi {
 namespace host {
 
 class ResourceHost;
+class ResourceMessageFilter;
+
+namespace internal {
+
+struct ResourceMessageFilterDeleteTraits {
+  static void Destruct(const ResourceMessageFilter* filter);
+};
+
+}  // namespace internal
 
 // This is the base class of resource message filters that can handle resource
 // messages on another thread. ResourceHosts can handle most messages
@@ -65,17 +74,27 @@ class ResourceHost;
 // AddFilter(make_scoped_refptr(new MyMessageFilter));
 class PPAPI_HOST_EXPORT ResourceMessageFilter
     : public ResourceMessageHandler,
-      public base::RefCountedThreadSafe<ResourceMessageFilter> {
+      public base::RefCountedThreadSafe<
+          ResourceMessageFilter, internal::ResourceMessageFilterDeleteTraits> {
  public:
+  enum DeletionThread {
+    // This object could be deleted on any thread.
+    DELETE_ON_ANY_THREAD,
+    // This object should be deleted on the same thread as it was created.
+    DELETE_ON_CREATION_THREAD
+  };
+
   // This object must be constructed on the same thread that a reply message
   // should be sent, i.e. the IO thread when constructed in the browser process
   // or the main thread when constructed in the renderer process. Since
   // ResourceMessageFilters are usually constructed in the constructor of the
   // owning ResourceHost, this will almost always be the case anyway.
-  ResourceMessageFilter();
+  // |deletion_thread| specifies on which thread the object should be deleted.
+  explicit ResourceMessageFilter(DeletionThread deletion_thread);
   // Test constructor. Allows you to specify the message loop which will be used
   // to dispatch replies on.
   ResourceMessageFilter(
+      DeletionThread deletion_thread,
       scoped_refptr<base::MessageLoopProxy> reply_thread_message_loop_proxy);
 
   // Called when a filter is added to a ResourceHost.
@@ -93,7 +112,6 @@ class PPAPI_HOST_EXPORT ResourceMessageFilter
       const IPC::Message& msg) OVERRIDE;
 
  protected:
-  friend class base::RefCountedThreadSafe<ResourceMessageFilter>;
   virtual ~ResourceMessageFilter();
 
   // If you want the message to be handled on another thread, return a non-null
@@ -102,10 +120,20 @@ class PPAPI_HOST_EXPORT ResourceMessageFilter
       const IPC::Message& message);
 
  private:
+  friend class base::DeleteHelper<ResourceMessageFilter>;
+  friend class base::RefCountedThreadSafe<
+      ResourceMessageFilter, internal::ResourceMessageFilterDeleteTraits>;
+  friend struct internal::ResourceMessageFilterDeleteTraits;
+
   // This method is posted to the target thread and runs the message handler.
   void DispatchMessage(const IPC::Message& msg,
                        HostMessageContext context);
 
+  void InternalDestruct() const;
+
+  // Set to NULL if the object can be deleted on any thread.
+  scoped_refptr<base::MessageLoopProxy> deletion_message_loop_proxy_;
+
   // Message loop to send resource message replies on. This will be the message
   // loop proxy of the IO thread for the browser process or the main thread for
   // the renderer process.