Remove last non-third_party typeofs on Mac.

ipc/ipc_message_macros.h

 // Copyright (c) 2012 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.
 
 // Defining IPC Messages
 //
 // Your IPC messages will be defined by macros inside of an XXX_messages.h
 // header file.  Most of the time, the system can automatically generate all
 // of messaging mechanism from these definitions, but sometimes some manual
 // coding is required.  In these cases, you will also have an XXX_messages.cc
@@ skipping 879 matching lines @@
 //   }
 
 
 #define IPC_BEGIN_MESSAGE_MAP(class_name, msg) \
   { \
     typedef class_name _IpcMessageHandlerClass ALLOW_UNUSED_TYPE; \
     void* param__ = NULL; \
     const IPC::Message& ipc_message__ = msg; \
     switch (ipc_message__.type()) {
 
-// gcc gives the following error now when using decltype so type typeof there:
-//   error: identifier 'decltype' will become a keyword in C++0x [-Werror=c++0x-compat]
-#if defined(OS_WIN)
-#define IPC_DECLTYPE decltype
-#else
-#define IPC_DECLTYPE typeof
-#endif
-
 #define IPC_BEGIN_MESSAGE_MAP_WITH_PARAM(class_name, msg, param)  \
   {                                                               \
     typedef class_name _IpcMessageHandlerClass ALLOW_UNUSED_TYPE; \
-    IPC_DECLTYPE(param) param__ = param;                          \
+    decltype(param) param__ = param;                              \
     const IPC::Message& ipc_message__ = msg;                      \
     switch (ipc_message__.type()) {
 
 #define IPC_MESSAGE_FORWARD(msg_class, obj, member_func)                       \
     case msg_class::ID: {                                                      \
         TRACK_RUN_IN_THIS_SCOPED_REGION(member_func);                          \
         if (!msg_class::Dispatch(&ipc_message__, obj, this, param__,           \
                                  &member_func))                                \
           ipc_message__.set_dispatch_error();                                  \
       }                                                                        \
@@ skipping 56 matching lines @@
 // equivalent without the #ifdef, VS2013 contains a bug where it is
 // over-aggressive in optimizing out #includes.  Putting the #ifdef is a
 // workaround for this bug.  See http://goo.gl/eGt2Fb for more details.
 // This can be removed once VS2013 is fixed.
 #ifdef IPC_MESSAGE_START
 // Clean up IPC_MESSAGE_START in this unguarded section so that the
 // XXX_messages.h files need not do so themselves.  This makes the
 // XXX_messages.h files easier to write.
 #undef IPC_MESSAGE_START
 #endif