Add a simple one shot and repeating timer API for Mojo.js.

gin/function_template.h

Index: gin/function_template.h
diff --git a/gin/function_template.h b/gin/function_template.h
index 91b3cdb0ce3a0785badd25a2780e2aba78233775..80eccc7525490689d0c96bcb70a656ddb8e46f98 100644
--- a/gin/function_template.h
+++ b/gin/function_template.h
@@ -179,7 +179,9 @@ struct Invoker<R, void, void, void, void> {
   inline static void Go(
       Arguments* args,
       const base::Callback<R()>& callback) {
-    args->Return(callback.Run());
+    R r = callback.Run();
+    LOG(ERROR) << "Setting return value to: " << r;
+    args->Return(r);
   }
 };
 template<>
@@ -210,6 +212,13 @@ inline bool GetNextArgument(Arguments* args, int create_flags, bool is_first,
   return true;
 }
 
+// It's common for clients to just need the isolate, so we make that easy.
+inline bool GetNextArgument(Arguments* args, int create_flags,
+                            bool is_first, v8::Isolate** result) {
+  *result = args->isolate();
+  return true;
+}
+
 
 // DispatchToCallback converts all the JavaScript arguments to C++ types and
 // invokes the base::Callback.