fix gprecise gcc build error

ipc/ipc_message.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.
 
 #ifndef IPC_IPC_MESSAGE_H_
 #define IPC_IPC_MESSAGE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 208 matching lines @@
   // reply message, so that when it's sent and we have the output parameters
   // we can log it.  As such, we set a flag on the sent message to not log it.
   void set_sync_log_data(LogData* data) const { log_data_ = data; }
   LogData* sync_log_data() const { return log_data_; }
   void set_dont_log() const { dont_log_ = true; }
   bool dont_log() const { return dont_log_; }
 #endif
 
   // Called at various points between send and receive to track message.
   void TraceMessageStep() {
-    TRACE_EVENT_ASYNC_BEGIN_STEP0("ipc", "IPC", header()->flags, NULL);
+    TRACE_EVENT_ASYNC_BEGIN_STEP0("ipc", "IPC", header()->flags, "step");
   }
 
  protected:
   friend class Channel;
   friend class MessageReplyDeserializer;
   friend class SyncMessage;
 
 #pragma pack(push, 4)
   struct Header : Pickle::Header {
     int32 routing;  // ID of the view that this message is destined for
@@ skipping 49 matching lines @@
   MSG_ROUTING_NONE = -2,
 
   // indicates a general message not sent to a particular tab.
   MSG_ROUTING_CONTROL = kint32max,
 };
 
 #define IPC_REPLY_ID 0xFFFFFFF0  // Special message id for replies
 #define IPC_LOGGING_ID 0xFFFFFFF1  // Special message id for logging
 
 #endif  // IPC_IPC_MESSAGE_H_