Add TypeTraits template for checking safe bitfields (WIP)

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

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 373 matching lines @@
 enum EEmptyCells {
     EmptyCellsShow, EmptyCellsHide
 };
 
 enum ECaptionSide {
     CaptionSideTop, CaptionSideBottom, CaptionSideLeft, CaptionSideRight
 };
 
 enum EListStylePosition { ListStylePositionOutside, ListStylePositionInside };
 
-// TODO(sashab): Add a static_assert when this is used in bitfields to ensure it
-// uses unsigned as the underlying type.
 enum class EVisibility : unsigned { Visible, Hidden, Collapse };
 
 enum ECursor {
     // The following must match the order in CSSValueKeywords.in.
     CURSOR_AUTO,
     CURSOR_CROSS,
     CURSOR_DEFAULT,
     CURSOR_POINTER,
     CURSOR_MOVE,
     CURSOR_VERTICAL_TEXT,
@@ skipping 214 matching lines @@
 
 enum AutoRepeatType {
     NoAutoRepeat,
     AutoFill,
     AutoFit
 };
 
 } // namespace blink
 
 #endif // ComputedStyleConstants_h