Another temporary CHECK to help track down crash in IPC.

ipc/ipc_message.cc

 // 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.
 
 #include "ipc/ipc_message.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/logging.h"
 #include "build/build_config.h"
 
@@ skipping 66 matching lines @@
 void Message::InitLoggingVariables() {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   received_time_ = 0;
   dont_log_ = false;
   log_data_ = NULL;
 #endif
 }
 
 Message& Message::operator=(const Message& other) {
   *static_cast<Pickle*>(this) = other;
+  // TODO(vtl): Remove once bug resolved.
+  CHECK(header()) << "crbug.com/357915";
 #if defined(OS_POSIX)
   file_descriptor_set_ = other.file_descriptor_set_;
 #endif
   return *this;
 }
 
 void Message::SetHeaderValues(int32 routing, uint32 type, uint32 flags) {
   // This should only be called when the message is already empty.
   DCHECK(payload_size() == 0);
 
@@ skipping 56 matching lines @@
 }
 
 void Message::EnsureFileDescriptorSet() {
   if (file_descriptor_set_.get() == NULL)
     file_descriptor_set_ = new FileDescriptorSet;
 }
 
 #endif
 
 }  // namespace IPC