Make V8ValueConverter.FromV8Value behave similarly to JSON.stringify

chrome/renderer/extensions/user_script_scheduler.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/extensions/user_script_scheduler.h"
 
 #include "base/bind.h"
 #include "base/message_loop.h"
 #include "chrome/common/extensions/extension_error_utils.h"
 #include "chrome/common/extensions/extension_manifest_constants.h"
@@ skipping 185 matching lines @@
 
       WebScriptSource source(WebString::fromUTF8(params.code));
       v8::HandleScope scope;
       v8::Persistent<v8::Context> persistent_context = v8::Context::New();
       v8::Local<v8::Context> context =
           v8::Local<v8::Context>::New(persistent_context);
       persistent_context.Dispose();
 
       scoped_ptr<content::V8ValueConverter> v8_converter(
           content::V8ValueConverter::create());
-      v8_converter->SetUndefinedAllowed(true);
+      v8_converter->SetUndefinedValueBehavior(
+          content::V8ValueConverter::CONVERT_TO_NULL);
       v8::Handle<v8::Value> script_value;
       if (params.in_main_world) {
         script_value = child_frame->executeScriptAndReturnValue(source);
       } else {
         WebKit::WebVector<v8::Local<v8::Value> > results;
         std::vector<WebScriptSource> sources;
         sources.push_back(source);
         child_frame->executeScriptInIsolatedWorld(
             dispatcher_->user_script_slave()->
                 GetIsolatedWorldIdForExtension(extension, child_frame),
             &sources.front(), sources.size(), EXTENSION_GROUP_CONTENT_SCRIPTS,
             &results);
         // We only expect one value back since we only pushed one source
         if (results.size() == 1 && !results[0].IsEmpty())
           script_value = results[0];
       }
       if (!script_value.IsEmpty()) {
         base::Value* base_val =
             v8_converter->FromV8Value(script_value, context);
-        execution_results.Append(base_val);
+        execution_results.Append(base_val ? base_val :
+                                            base::Value::CreateNullValue());
         script_value.Clear();
       }
     } else {
       child_frame->document().insertUserStyleSheet(
           WebString::fromUTF8(params.code),
           // Author level is consistent with WebView::addUserStyleSheet.
           WebDocument::UserStyleAuthorLevel);
     }
   }
 
@@ skipping 14 matching lines @@
 
   for (WebFrame* child_frame = parent_frame->firstChild(); child_frame;
        child_frame = child_frame->nextSibling()) {
     frames_vector->push_back(child_frame);
     GetAllChildFrames(child_frame, frames_vector);
   }
   return true;
 }
 
 }  // namespace extensions