PPAPI: Remove threading options; it's always on

ppapi/proxy/plugin_globals.h

Index: ppapi/proxy/plugin_globals.h
diff --git a/ppapi/proxy/plugin_globals.h b/ppapi/proxy/plugin_globals.h
index 4da6d5fbbc28c0e964f9b39aa35ce3cd4399b98a..37fdc1aac55b4218f9bb3a355234323cdf5c68ac 100644
--- a/ppapi/proxy/plugin_globals.h
+++ b/ppapi/proxy/plugin_globals.h
@@ -114,10 +114,6 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
   // The embedder should call this function when the command line is known.
   void set_command_line(const std::string& c) { command_line_ = c; }
 
-  // Sets whether threadsafety is supported. Defaults to whether the
-  // ENABLE_PEPPER_THREADING build flag is set.
-  void set_enable_threading(bool enable) { enable_threading_ = enable; }
-
  private:
   class BrowserSender;
 
@@ -131,7 +127,6 @@ class PPAPI_PROXY_EXPORT PluginGlobals : public PpapiGlobals {
   PluginVarTracker plugin_var_tracker_;
   scoped_refptr<CallbackTracker> callback_tracker_;
 
-  bool enable_threading_;  // Indicates whether we'll use the lock.
   base::Lock proxy_lock_;
 
   scoped_ptr<base::ThreadLocalStorage::Slot> msg_loop_slot_;