gin: Create a DataObjectBuilder class to help create simple data objects.

gin/data_object_builder.cc

Index: gin/data_object_builder.cc
diff --git a/gin/data_object_builder.cc b/gin/data_object_builder.cc
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+// Copyright 2017 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 "gin/data_object_builder.h"
+
+namespace gin {
+
+DataObjectBuilder::DataObjectBuilder(v8::Isolate* isolate)
+    : isolate_(isolate),
+      context_(isolate->GetCurrentContext()),

[Devlin, 2017/04/26 15:50:31]

Would it be better to pass in the context and get the isolate from that, rather
than the other way around?  That way we have an explicit context for the
SetDataProperty() calls.

[jbroman, 2017/04/26 17:47:31]

It's a bit of a lie because v8::Object::New already uses the current context. To
make that properly true we'd need a v8::Context::Scope, but the caller is in a
good position to ensure that one is in place (and probably already has).

I don't feel strongly, so I could budge on this if you feel strongly.

[Devlin, 2017/04/26 18:30:23]

Ah, good point.  This is fine.

On that note, naively, it seems to me we should have a version of
v8::Object::New that takes a context, since most things that result in
context-related happenings - getting/setting/executing - now seem to.  jochen@,
can you shed some light on why we don't do this?

+      object_(v8::Object::New(isolate)) {}
+
+}  // namespace gin