[LayoutNG] Initial support for multicol, introducing NGBlockBreakToken.

third_party/WebKit/Source/core/layout/ng/ng_break_token.h

 // Copyright 2016 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 NGBreakToken_h
 #define NGBreakToken_h
 
 #include "core/CoreExport.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class CORE_EXPORT NGBreakToken
     : public GarbageCollectedFinalized<NGBreakToken> {
  public:
-  NGBreakToken() {}
+  virtual ~NGBreakToken() {}
 
-  DEFINE_INLINE_TRACE() {}
+  enum NGBreakTokenType { kBlockBreakToken, kTextBreakToken };
+  NGBreakTokenType Type() const { return static_cast<NGBreakTokenType>(type_); }
+
+  DEFINE_INLINE_VIRTUAL_TRACE() {}
+
+ protected:
+  NGBreakToken(NGBreakTokenType type) : type_(type) {}
+
+ private:
+  unsigned type_ : 1;
 };
-}
 
-#endif
+}  // namespace blink
+
+#endif  // NGBreakToken_h