[LayoutNG] Initial support for multicol, introducing NGBlockBreakToken.

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

+// 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 NGBlockBreakToken_h
+#define NGBlockBreakToken_h
+
+#include "core/layout/ng/ng_break_token.h"
+#include "platform/LayoutUnit.h"
+
+namespace blink {
+
+class NGBlockNode;
+
+class NGBlockBreakToken : public NGBreakToken {
+ public:
+  NGBlockBreakToken(NGBlockNode* node, LayoutUnit break_offset)
+      : NGBreakToken(kBlockBreakToken),
+        node_(node),
+        break_offset_(break_offset) {}
+
+  NGBlockNode& InputNode() const { return *node_.get(); }
+  LayoutUnit BreakOffset() const { return break_offset_; }
+
+  DEFINE_INLINE_VIRTUAL_TRACE() {
+    NGBreakToken::trace(visitor);
+    visitor->trace(node_);
+  }
+
+ private:
+  Member<NGBlockNode> node_;
+  LayoutUnit break_offset_;
+};
+
+DEFINE_TYPE_CASTS(NGBlockBreakToken,
+                  NGBreakToken,
+                  token,
+                  token->Type() == NGBreakToken::kBlockBreakToken,
+                  token.Type() == NGBreakToken::kBlockBreakToken);
+
+}  // namespace blink
+
+#endif  // NGBlockBreakToken_h