Make V8ValueConverter.FromV8Value behave similarly to JSON.stringify

chrome/renderer/extensions/user_script_scheduler.cc

Index: chrome/renderer/extensions/user_script_scheduler.cc
diff --git a/chrome/renderer/extensions/user_script_scheduler.cc b/chrome/renderer/extensions/user_script_scheduler.cc
index 3d98aea437cfcd075ca54593e7576ccfec1ca147..fec5a98748f03aa9c8525a51e226732fac9fb2bd 100644
--- a/chrome/renderer/extensions/user_script_scheduler.cc
+++ b/chrome/renderer/extensions/user_script_scheduler.cc
@@ -203,7 +203,6 @@ void UserScriptScheduler::ExecuteCodeImpl(
 
       scoped_ptr<content::V8ValueConverter> v8_converter(
           content::V8ValueConverter::create());
-      v8_converter->SetUndefinedAllowed(true);
       v8::Handle<v8::Value> script_value;
       if (params.in_main_world) {
         script_value = child_frame->executeScriptAndReturnValue(source);
@@ -223,7 +222,10 @@ void UserScriptScheduler::ExecuteCodeImpl(
       if (!script_value.IsEmpty()) {
         base::Value* base_val =
             v8_converter->FromV8Value(script_value, context);
-        execution_results.Append(base_val);
+        // Always append an execution result (i.e. no result == null result) so
+        // that |execution_results| lines up with the frames.
+        execution_results.Append(base_val ? base_val :
+                                            base::Value::CreateNullValue());
         script_value.Clear();
       }
     } else {