IDL: Add build target for IDL dictionary impl generation in core

Source/core/testing/TestingDictionary.idl

Index: Source/core/testing/TestingDictionary.idl
diff --git a/Source/core/testing/TestingDictionary.idl b/Source/core/testing/TestingDictionary.idl
new file mode 100644
index 0000000000000000000000000000000000000000..3e8fba274050b7fa48a7bed91ce7d668d228a449
--- /dev/null
+++ b/Source/core/testing/TestingDictionary.idl
@@ -0,0 +1,13 @@
+// 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.
+
+[
+    GarbageCollected
+] dictionary TestingDictionary {
+    long longMember;
+    DOMString stringMember = "defaultStringValue";
+    boolean? booleanOrNullMember = null;
+    double? doubleOrNullMember;
+    sequence<DOMString> stringSequenceMember;
+};