Enable Pepper threading on canary.

webkit/plugins/plugin_switches.cc

Index: webkit/plugins/plugin_switches.cc
diff --git a/webkit/plugins/plugin_switches.cc b/webkit/plugins/plugin_switches.cc
index 98a43c255136caa107023e1390056341b3037774..9116c55d29d30fb52333002d6d5ae978a5a065f1 100644
--- a/webkit/plugins/plugin_switches.cc
+++ b/webkit/plugins/plugin_switches.cc
@@ -18,6 +18,9 @@ const char kPpapiFlashArgs[] = "ppapi-flash-args";
 // Set to true to allow threadsafety support in native Pepper plugins.
 const char kEnablePepperThreading[] = "enable-pepper-threading";
 
+// Set to true to not allow threadsafety support in native Pepper plugins.
+const char kDisablePepperThreading[] = "disable-pepper-threading";
+
 #if defined(OS_WIN)
 // Used by the plugins_test when testing the older WMP plugin to force the new
 // plugin to not get loaded.