Add dart_invoke to tonic for calls into App code.

sky/engine/tonic/dart_invoke.h

Index: sky/engine/tonic/dart_invoke.h
diff --git a/sky/engine/tonic/dart_invoke.h b/sky/engine/tonic/dart_invoke.h
new file mode 100644
index 0000000000000000000000000000000000000000..a673779156da7f46c92e7fc33380187aee9645c4
--- /dev/null
+++ b/sky/engine/tonic/dart_invoke.h
@@ -0,0 +1,23 @@
+// 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_INVOKE_H_
+#define SKY_ENGINE_TONIC_DART_INVOKE_H_
+
+#include "dart/runtime/include/dart_api.h"
+
+namespace blink {
+
+bool DartInvokeNamedAppClosure(Dart_Handle target, Dart_Handle name,
+                               int number_of_arguments,
+                               Dart_Handle* arguments);
+
+bool DartInvokeAppClosure(Dart_Handle closure,
+                          int number_of_arguments,
+                          Dart_Handle* arguments);
+
+}  // namespace blink
+
+#endif  // SKY_ENGINE_TONIC_DART_INVOKE_H_
+