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

base/bind_internal_win.h.pump

 $$ This is a pump file for generating file templates.  Pump is a python
 $$ script that is part of the Google Test suite of utilities.  Description
 $$ can be found here:
 $$
 $$ http://code.google.com/p/googletest/wiki/PumpManual
 $$
 
 $var MAX_ARITY = 6
 
 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
@@ skipping 22 matching lines @@
 $for ARITY [[
 $range ARG 1..ARITY
 
 // __stdcall Function: Arity $(ARITY).
 template <typename R[[]]
 $if ARITY > 0[[, ]] $for ARG , [[typename X$(ARG)]]>
 struct FunctionTraits<R(__stdcall *)($for ARG , [[X$(ARG)]])> {
   typedef R (*NormalizedSig)($for ARG , [[X$(ARG)]]);
   typedef false_type IsMethod;
 
+  typedef R Return;
+
 $if ARITY > 0 [[
 
   // Target type for each bound parameter.
 
 $for ARG [[
   typedef X$(ARG) B$(ARG);
 
 ]]  $$ for ARG
 ]]  $$ if ARITY > 0
 };
 
 // __fastcall Function: Arity $(ARITY).
 template <typename R[[]]
 $if ARITY > 0[[, ]] $for ARG , [[typename X$(ARG)]]>
 struct FunctionTraits<R(__fastcall *)($for ARG , [[X$(ARG)]])> {
   typedef R (*NormalizedSig)($for ARG , [[X$(ARG)]]);
   typedef false_type IsMethod;
 
+  typedef R Return;
+
 $if ARITY > 0 [[
 
   // Target type for each bound parameter.
 
 $for ARG [[
   typedef X$(ARG) B$(ARG);
 
 ]]  $$ for ARG
 ]]  $$ if ARITY > 0
 };
 
 ]]  $$for ARITY
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // !defined(ARCH_CPU_X86_64)
 
 #endif  // BASE_BIND_INTERNAL_WIN_H_