Revert 189518 "PPAPI: Remove threading options; it's always on"

trunk/src/ppapi/proxy/plugin_globals.h

Index: trunk/src/ppapi/proxy/plugin_globals.h
===================================================================
--- trunk/src/ppapi/proxy/plugin_globals.h	(revision 189681)
+++ trunk/src/ppapi/proxy/plugin_globals.h	(working copy)
@@ -114,6 +114,10 @@
   // 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;
 
@@ -127,6 +131,7 @@
   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_;