Make IPC::Channel::Listener:OnMessageReceived have a return value indicating ...

chrome/plugin/plugin_thread.cc

Index: chrome/plugin/plugin_thread.cc
===================================================================
--- chrome/plugin/plugin_thread.cc	(revision 70108)
+++ chrome/plugin/plugin_thread.cc	(working copy)
@@ -128,13 +128,16 @@
   return lazy_tls.Pointer()->Get();
 }
 
-void PluginThread::OnControlMessageReceived(const IPC::Message& msg) {
+bool PluginThread::OnControlMessageReceived(const IPC::Message& msg) {
+  bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(PluginThread, msg)
     IPC_MESSAGE_HANDLER(PluginProcessMsg_CreateChannel, OnCreateChannel)
     IPC_MESSAGE_HANDLER(PluginProcessMsg_PluginMessage, OnPluginMessage)
     IPC_MESSAGE_HANDLER(PluginProcessMsg_NotifyRenderersOfPendingShutdown,
                         OnNotifyRenderersOfPendingShutdown)
+    IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
+  return handled;
 }
 
 void PluginThread::OnCreateChannel(int renderer_id,