Moved the following IPC messages used by the chrome NPAPI plugin installer out of content

chrome/browser/plugin_observer.h

Index: chrome/browser/plugin_observer.h
===================================================================
--- chrome/browser/plugin_observer.h	(revision 98657)
+++ chrome/browser/plugin_observer.h	(working copy)
@@ -22,11 +22,13 @@
   // IPC::Channel::Listener implementation.
   virtual bool OnMessageReceived(const IPC::Message& message);
 
+  // Helper function to handle missing plugin status.
+  static void OnMissingPluginStatus(int status,
+                                    int render_process_id,
+                                    int render_view_id,
+                                    int window);
+
  private:
-  // Returns the PluginInstallerInfoBarDelegate, creating it if necessary.
-  PluginInstallerInfoBarDelegate* GetPluginInstaller();
-
-  void OnMissingPluginStatus(int status);
   void OnCrashedPlugin(const FilePath& plugin_path);
   void OnBlockedOutdatedPlugin(const string16& name, const GURL& update_url);