Expose requireAsync method and make it more robust

extensions/renderer/module_system.h

Index: extensions/renderer/module_system.h
diff --git a/extensions/renderer/module_system.h b/extensions/renderer/module_system.h
index 51ecc95f91cd49c9febe7109cd33cc747ecf6e5e..b4cc964c3dfa722c4ae21643b9abf94a956d3e23 100644
--- a/extensions/renderer/module_system.h
+++ b/extensions/renderer/module_system.h
@@ -192,8 +192,9 @@ class ModuleSystem : public ObjectBackedNativeHandler,
   // NativeHandler implementation which returns the private area of an Object.
   void Private(const v8::FunctionCallbackInfo<v8::Value>& args);
 
-  // Loads and runs a Javascript module.
-  v8::Handle<v8::Value> LoadModule(const std::string& module_name);
+  // Runs a Javascript module.
+  v8::Handle<v8::Value> LoadModule(const std::string& module_name,
+                                   v8::Handle<v8::Value> module_source);
 
   // Invoked when a module is loaded in response to a requireAsync call.
   // Resolves |resolver| with |value|.