Support binding WeakPtr<> to methods with void return types.

base/template_util.h

Index: base/template_util.h
diff --git a/base/template_util.h b/base/template_util.h
index e48af9183b5a5e3255f169eb6ed31b7d6c0885e1..66e6a6106140c59b12d469f59a0f17424a85bbfd 100644
--- a/base/template_util.h
+++ b/base/template_util.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
@@ -37,6 +37,9 @@ template <class T> struct is_non_const_reference : false_type {};
 template <class T> struct is_non_const_reference<T&> : true_type {};
 template <class T> struct is_non_const_reference<const T&> : false_type {};
 
+template <class T> struct is_void : false_type {};
+template <> struct is_void<void> : true_type {};
+
 namespace internal {
 
 // Types YesType and NoType are guaranteed such that sizeof(YesType) <