Move the common child process messages into their own file.

chrome/common/plugin_messages_internal.h

Index: chrome/common/plugin_messages_internal.h
===================================================================
--- chrome/common/plugin_messages_internal.h	(revision 77193)
+++ chrome/common/plugin_messages_internal.h	(working copy)
@@ -36,23 +36,7 @@
 // shutdown, so we don't mistake it for a crash.
 IPC_MESSAGE_CONTROL0(PluginProcessMsg_NotifyRenderersOfPendingShutdown)
 
-// The following messages are used by all child processes, even though they
-// are listed under PluginProcess.  It seems overkill to define ChildProcess.
-// Tells the child process it should stop.
-IPC_MESSAGE_CONTROL0(PluginProcessMsg_AskBeforeShutdown)
 
-// Sent in response to PluginProcessHostMsg_ShutdownRequest to tell the child
-// process that it's safe to shutdown.
-IPC_MESSAGE_CONTROL0(PluginProcessMsg_Shutdown)
-
-#if defined(IPC_MESSAGE_LOG_ENABLED)
-// Tell the child process to begin or end IPC message logging.
-// Like above, this is used by all ChildProcesses.
-IPC_MESSAGE_CONTROL1(PluginProcessMsg_SetIPCLoggingEnabled,
-                     bool /* on or off */)
-#endif
-
-
 //-----------------------------------------------------------------------------
 // PluginProcessHost messages
 // These are messages sent from the plugin process to the browser process.
@@ -63,8 +47,6 @@
 IPC_SYNC_MESSAGE_CONTROL0_1(PluginProcessHostMsg_GetPluginFinderUrl,
                             std::string /* plugin finder URL */)
 
-IPC_MESSAGE_CONTROL0(PluginProcessHostMsg_ShutdownRequest)
-
 // Allows a chrome plugin loaded in a plugin process to send arbitrary
 // data to an instance of the same plugin loaded in the browser process.
 IPC_MESSAGE_CONTROL1(PluginProcessHostMsg_PluginMessage,