Make TextDecoration an enum class.

third_party/WebKit/Source/core/style/AppliedTextDecoration.cpp

 // 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.
 
 #include "core/style/AppliedTextDecoration.h"
 
 namespace blink {
 
 AppliedTextDecoration::AppliedTextDecoration(TextDecoration line,
                                              TextDecorationStyle style,
                                              Color color)
-    : lines_(line), style_(style), color_(color) {}
+    : lines_(static_cast<unsigned>(line)), style_(style), color_(color) {}
 
 bool AppliedTextDecoration::operator==(const AppliedTextDecoration& o) const {
   return color_ == o.color_ && lines_ == o.lines_ && style_ == o.style_;
 }
 
 }  // namespace blink