gin: Use V8 Maybe APIs

gin/converter.h

Index: gin/converter.h
diff --git a/gin/converter.h b/gin/converter.h
index fa3367dff46eed3a87f5912fd493f0961b88027f..f882980d8b2f5207c50e58195dd9f5dd13ae5290 100644
--- a/gin/converter.h
+++ b/gin/converter.h
@@ -14,6 +14,15 @@
 
 namespace gin {
 
+template<typename KeyType>
+bool SetProperty(v8::Isolate* isolate,
+                 v8::Local<v8::Object> object,
+                 KeyType key,
+                 v8::Local<v8::Value> value) {
+  auto maybe = object->Set(isolate->GetCurrentContext(), key, value);
+  return !maybe.IsNothing() && maybe.FromJust();
+}
+
 template<typename T, typename Enable = void>
 struct Converter {};
 
@@ -145,12 +154,16 @@ struct GIN_EXPORT Converter<v8::Handle<v8::Value> > {
 
 template<typename T>
 struct Converter<std::vector<T> > {
+  // If this function fails to set an element due to an exception, this returns
+  // an empty handle.
   static v8::Handle<v8::Value> ToV8(v8::Isolate* isolate,
                                     const std::vector<T>& val) {
     v8::Handle<v8::Array> result(
         v8::Array::New(isolate, static_cast<int>(val.size())));
     for (size_t i = 0; i < val.size(); ++i) {
-      result->Set(static_cast<int>(i), Converter<T>::ToV8(isolate, val[i]));
+      if (!SetProperty(isolate, result, static_cast<int>(i),
+                       Converter<T>::ToV8(isolate, val[i])))
+        return v8::Handle<v8::Value>();

[jochen (gone - plz use gerrit), 2015/04/28 11:14:20]

we shouldn't return empty handles but MaybeLocal<> values

[bashi, 2015/05/01 03:50:35]

Changing return type requires 3-way CLs.
1. Add Maybe version of Converter::ToV8()
2. Use them in other components which depend on gin
3. Remove the current ToV8()

Does this sound reasonable? Then I'll do that.

Also, should we change all Converter::ToV8() to return MaybeLocal for
consistency?

     }
     return result;
   }