Move AppliedTextDecorationList to its own file.

third_party/WebKit/Source/core/style/AppliedTextDecorationList.h

Index: third_party/WebKit/Source/core/style/AppliedTextDecorationList.h
diff --git a/third_party/WebKit/Source/core/style/AppliedTextDecorationList.h b/third_party/WebKit/Source/core/style/AppliedTextDecorationList.h
new file mode 100644
index 0000000000000000000000000000000000000000..c2ad4ea1fa604578cc272c616395b0ae77803639
--- /dev/null
+++ b/third_party/WebKit/Source/core/style/AppliedTextDecorationList.h
@@ -0,0 +1,17 @@
+// Copyright 2017 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 AppliedTextDecorationList_h
+#define AppliedTextDecorationList_h
+
+#include "core/style/AppliedTextDecoration.h"
+#include "platform/wtf/RefVector.h"
+
+namespace blink {
+
+typedef RefVector<AppliedTextDecoration> AppliedTextDecorationList;
+
+}  // namespace blink
+
+#endif  // AppliedTextDecorationList_h