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

sky/engine/bindings-dart/core/dart/DartPersistentValue.h

Index: sky/engine/bindings-dart/core/dart/DartPersistentValue.h
diff --git a/sky/engine/platform/LayoutTestSupport.h b/sky/engine/bindings-dart/core/dart/DartPersistentValue.h
similarity index 74%
copy from sky/engine/platform/LayoutTestSupport.h
copy to sky/engine/bindings-dart/core/dart/DartPersistentValue.h
index 72ceaf4fe1e0b3684086703f569f25eb12707959..db92b4e5a71663ec38855c178ef6964d52139f7c 100644
--- a/sky/engine/platform/LayoutTestSupport.h
+++ b/sky/engine/bindings-dart/core/dart/DartPersistentValue.h
@@ -28,21 +28,29 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef SKY_ENGINE_PLATFORM_LAYOUTTESTSUPPORT_H_
-#define SKY_ENGINE_PLATFORM_LAYOUTTESTSUPPORT_H_
+#ifndef DartPersistentValue_h
+#define DartPersistentValue_h
 
-#include "sky/engine/platform/PlatformExport.h"
+#include "bindings/core/dart/DartIsolateDestructionObserver.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/RefPtr.h"
+#include <dart_api.h>
 
 namespace blink {
 
-class LayoutTestSupport {
+class DartPersistentValue : public DartIsolateDestructionObserver {
+    WTF_MAKE_NONCOPYABLE(DartPersistentValue);
 public:
-    PLATFORM_EXPORT static bool isRunningLayoutTest();
-    PLATFORM_EXPORT static void setIsRunningLayoutTest(bool);
-    PLATFORM_EXPORT static bool isFontAntialiasingEnabledForTest();
-    PLATFORM_EXPORT static void setFontAntialiasingEnabledForTest(bool);
+    explicit DartPersistentValue(Dart_Handle value);
+    ~DartPersistentValue();
+
+    Dart_PersistentHandle value() const { return m_value; }
+    void clear();
+
+private:
+    Dart_PersistentHandle m_value;
 };
 
-} // namespace blink
+}
 
-#endif  // SKY_ENGINE_PLATFORM_LAYOUTTESTSUPPORT_H_
+#endif // DartPersistentValue_h