[LayoutNG] Add fields required for new multi-col approach.

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;
 
+// Represents a break token for a block node.
 class NGBlockBreakToken : public NGBreakToken {
  public:
+  // Creates a break token for a node which did fragment, and can potentially
+  // produce more fragments.
+  NGBlockBreakToken(NGBlockNode* node,
+                    LayoutUnit used_block_size,
+                    HeapVector<Member<NGBreakToken>>& child_break_tokens)
+      : NGBreakToken(kBlockBreakToken, /* is_finished */ false, node),
+        used_block_size_(used_block_size) {
+    child_break_tokens_.swap(child_break_tokens);
+  }
+
+  // Creates a break token for a node which cannot produce any more fragments.
+  explicit NGBlockBreakToken(NGBlockNode* node)
+      : NGBreakToken(kBlockBreakToken, /* is_finished */ true, node) {}
+
+  // TODO(ikilpatrick): Remove this constructor and break_offset once we've
+  // switched to new multi-col approach.
   NGBlockBreakToken(NGBlockNode* node, LayoutUnit break_offset)
-      : NGBreakToken(kBlockBreakToken),
-        node_(node),
+      : NGBreakToken(kBlockBreakToken, false, node),
         break_offset_(break_offset) {}
 
-  NGBlockNode& InputNode() const { return *node_.get(); }
+  // Represents the amount of block size used in previous fragments.
+  //
+  // E.g. if the layout block specifies a block size of 200px, and the previous
+  // fragments of this block used 150px (used block size), the next fragment
+  // should have a size of 50px (assuming no additional fragmentation).
+  LayoutUnit UsedBlockSize() const { return used_block_size_; }
+
+  // The break tokens for children of the layout node.
+  //
+  // This is used to resume layout of any children which fragmented, it may
+  // contain "finished" break tokens so we know which children to skip for the
+  // next fragment.
+  const HeapVector<Member<NGBreakToken>>& ChildBreakTokens() const {
+    return child_break_tokens_;
+  }
+
+  // TODO(ikilpatrick): Remove this accessor.
   LayoutUnit BreakOffset() const { return break_offset_; }
 
   DEFINE_INLINE_VIRTUAL_TRACE() {
     NGBreakToken::trace(visitor);
-    visitor->trace(node_);
+    visitor->trace(child_break_tokens_);
   }
 
  private:
-  Member<NGBlockNode> node_;
   LayoutUnit break_offset_;
+  LayoutUnit used_block_size_;
+  HeapVector<Member<NGBreakToken>> child_break_tokens_;
 };
 
 DEFINE_TYPE_CASTS(NGBlockBreakToken,
                   NGBreakToken,
                   token,
                   token->Type() == NGBreakToken::kBlockBreakToken,
                   token.Type() == NGBreakToken::kBlockBreakToken);
 
 }  // namespace blink
 
 #endif  // NGBlockBreakToken_h