Import Dart bindings as of Blink r188698. This merely copies the files over and does not attach any…

sky/engine/bindings-dart/common/Nullable.h

 // Copyright 2014 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_BINDINGS_CORE_V8_NULLABLE_H_
-#define SKY_ENGINE_BINDINGS_CORE_V8_NULLABLE_H_
+#ifndef Nullable_h
+#define Nullable_h
 
-#include "sky/engine/platform/heap/Handle.h"
-#include "sky/engine/wtf/Assertions.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Assertions.h"
 
 namespace blink {
 
 template <typename T>
 class Nullable {
     DISALLOW_ALLOCATION();
 public:
     Nullable()
         : m_value()
         , m_isNull(true) { }
@@ skipping 24 matching lines @@
 
     // See comment in RefPtr.h about what UnspecifiedBoolType is.
     typedef const T* UnspecifiedBoolType;
     operator UnspecifiedBoolType() const { return m_isNull ? 0 : &m_value; }
 
     bool operator==(const Nullable& other) const
     {
         return (m_isNull && other.m_isNull) || (!m_isNull && !other.m_isNull && m_value == other.m_value);
     }
 
+    void trace(Visitor* visitor)
+    {
+        TraceIfNeeded<T>::trace(visitor, &m_value);
+    }
+
 private:
     T m_value;
     bool m_isNull;
 };
 
 } // namespace blink
 
-#endif  // SKY_ENGINE_BINDINGS_CORE_V8_NULLABLE_H_
+#endif // Nullable_h