Wholesale move sky/engine/tonic to tonic

tonic/dart_persistent_value.h

Index: tonic/dart_persistent_value.h
diff --git a/tonic/dart_persistent_value.h b/tonic/dart_persistent_value.h
new file mode 100644
index 0000000000000000000000000000000000000000..c6215c4b077a42f11febc19f94f0846e591118bd
--- /dev/null
+++ b/tonic/dart_persistent_value.h
@@ -0,0 +1,43 @@
+// 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_TONIC_DART_PERSISTENT_VALUE_H_
+#define SKY_ENGINE_TONIC_DART_PERSISTENT_VALUE_H_
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "dart/runtime/include/dart_api.h"
+
+namespace blink {
+class DartState;
+
+// DartPersistentValue is a bookkeeping class to help pair calls to
+// Dart_NewPersistentHandle with Dart_DeletePersistentHandle. Consider using
+// this class instead of holding a Dart_PersistentHandle directly so that you
+// don't leak the Dart_PersistentHandle.
+class DartPersistentValue {
+ public:
+  DartPersistentValue();
+  DartPersistentValue(DartState* dart_state, Dart_Handle value);
+  ~DartPersistentValue();
+
+  Dart_PersistentHandle value() const { return value_; }
+  bool is_empty() const { return !value_; }
+
+  void Set(DartState* dart_state, Dart_Handle value);
+  void Clear();
+  Dart_Handle Release();
+
+  const base::WeakPtr<DartState>& dart_state() const { return dart_state_; }
+
+ private:
+  base::WeakPtr<DartState> dart_state_;
+  Dart_PersistentHandle value_;
+
+  DISALLOW_COPY_AND_ASSIGN(DartPersistentValue);
+};
+
+}  // namespace blink
+
+#endif  // SKY_ENGINE_TONIC_DART_PERSISTENT_VALUE_H_