Add DartController and friends

sky/engine/core/script/dart_dependency_catcher.h

Index: sky/engine/core/script/dart_dependency_catcher.h
diff --git a/sky/engine/core/script/dart_dependency_catcher.h b/sky/engine/core/script/dart_dependency_catcher.h
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+++ b/sky/engine/core/script/dart_dependency_catcher.h
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+// 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.
+
+#ifndef SKY_ENGINE_CORE_SCRIPT_DEPENDENCY_CATCHER_H_
+#define SKY_ENGINE_CORE_SCRIPT_DEPENDENCY_CATCHER_H_
+
+#include "base/macros.h"
+#include "sky/engine/wtf/HashSet.h"
+
+namespace blink {
+class DartLoader;
+
+// A base class to represent a dependency.
+class DartDependency {
+};
+
+// To catch the dependencies for a library, put a DartDependencyCatcher on the
+// stack during the call to Dart_LoadLibrary.
+class DartDependencyCatcher {
+ public:
+  explicit DartDependencyCatcher(DartLoader& loader);
+  ~DartDependencyCatcher();
+
+  void AddDependency(DartDependency* dependency);
+  const HashSet<DartDependency*>& dependencies() const { return dependencies_; }
+
+ private:
+  DartLoader& loader_;
+  HashSet<DartDependency*> dependencies_;
+
+  DISALLOW_COPY_AND_ASSIGN(DartDependencyCatcher);
+};
+
+}  // namespace blink
+
+#endif  // SKY_ENGINE_CORE_SCRIPT_DEPENDENCY_CATCHER_H_