Const-ify RefCountedThreadSafe::AddRef and Release.

base/message_loop_proxy.h

Index: base/message_loop_proxy.h
diff --git a/base/message_loop_proxy.h b/base/message_loop_proxy.h
index 5d6708e0926fa6716298b7ec7a13f49803c332b5..4d38155ec7435d2331c81778eff8ad600171b78a 100644
--- a/base/message_loop_proxy.h
+++ b/base/message_loop_proxy.h
@@ -64,11 +64,11 @@ class MessageLoopProxy
 
   // Called when the proxy is about to be deleted. Subclasses can override this
   // to provide deletion on specific threads.
-  virtual void OnDestruct();
+  virtual void OnDestruct() const;
 };
 
 struct MessageLoopProxyTraits {
-  static void Destruct(MessageLoopProxy* proxy) {
+  static void Destruct(const MessageLoopProxy* proxy) {
     proxy->OnDestruct();
   }
 };