Adding --disable-plugins-discovery command line switch to not load third-party plugins from common …

webkit/plugins/npapi/plugin_list_mac.mm

Index: webkit/plugins/npapi/plugin_list_mac.mm
===================================================================
--- webkit/plugins/npapi/plugin_list_mac.mm	(revision 204507)
+++ webkit/plugins/npapi/plugin_list_mac.mm	(working copy)
@@ -274,7 +274,11 @@
   return false;
 }
 
-void PluginList::GetPluginDirectories(std::vector<base::FilePath>* plugin_dirs) {
+void PluginList::GetPluginDirectories(
+    std::vector<base::FilePath>* plugin_dirs) {
+  if (PluginList::plugins_discovery_disabled_)
+    return;
+
   // Load from the user's area
   GetPluginCommonDirectory(plugin_dirs, true);