Add DartController and friends

sky/engine/core/script/dart_dependency_catcher.cc

+// Copyright 2015 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 "sky/engine/config.h"
+#include "sky/engine/core/script/dart_dependency_catcher.h"
+
+#include "sky/engine/core/script/dart_loader.h"
+
+namespace blink {
+
+DartDependencyCatcher::DartDependencyCatcher(DartLoader& loader) : loader_(loader) {
+  loader_.set_dependency_catcher(this);
+}
+
+DartDependencyCatcher::~DartDependencyCatcher() {
+  loader_.set_dependency_catcher(nullptr);
+}
+
+void DartDependencyCatcher::AddDependency(DartDependency* dependency) {
+  dependencies_.add(dependency);
+}
+
+}  // namespace blink