Remove IPC_BEGIN_MESSAGE_MAP_EX macro since r270839 made all bad IPCs kill their child processes.

content/browser/browser_child_process_host_impl.cc

Index: content/browser/browser_child_process_host_impl.cc
===================================================================
--- content/browser/browser_child_process_host_impl.cc	(revision 271040)
+++ content/browser/browser_child_process_host_impl.cc	(working copy)
@@ -261,6 +261,10 @@
 void BrowserChildProcessHostImpl::OnBadMessageReceived(
     const IPC::Message& message) {
   HistogramBadMessageTerminated(data_.process_type);
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableKillAfterBadIPC)) {
+    return;
+  }
   base::KillProcess(GetHandle(), RESULT_CODE_KILLED_BAD_MESSAGE, false);
 }