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

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 NGLayoutInputNode;

[Gleb Lanbin, 2017/02/15 19:21:39]

can we just include NGLayoutInputNode?
https://google.github.io/styleguide/cppguide.html#Forward_Declarationss

[mstensho (USE GERRIT), 2017/02/15 21:25:38]

Chromium style thankfully overrides this, though:

https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md...

Compilation times just keep growing. :(

[ikilpatrick, 2017/02/16 17:01:30]

We should try and push for keeping the forward declare rule in a pre-condition
check... :/

+
+// A break token is a continuation token for layout. A single layout input node
+// can have multiple fragments asssociated with it.
+//
+// Each fragment has a break token which can be used to determine if a layout
+// input node has been "exhausted" of fragments, and optionally used to produce
+// the next fragment in the chain.
+//
+// See CSS Fragmentation (https://drafts.csswg.org/css-break/) for a detailed
+// description of different types of breaks which can occur in CSS.
+//
+// Each layout algorithm which can fragment, e.g. block-flow can optionally
+// accept a break token. For example:
+//
+// NGLayoutInputNode* node = ...;
+// NGPhysicalFragment* fragment = node->Layout(space);
+// DCHECK(!fragment->BreakToken()->IsFinished());
+// NGPhysicalFragment* fragment2 = node->Layout(space, fragment->BreakToken());
+//
+// The break token should encapsulate enough information to "resume" the layout.
 class CORE_EXPORT NGBreakToken
     : public GarbageCollectedFinalized<NGBreakToken> {
  public:
   virtual ~NGBreakToken() {}
 
   enum NGBreakTokenType { kBlockBreakToken, kTextBreakToken };
   NGBreakTokenType Type() const { return static_cast<NGBreakTokenType>(type_); }
 
-  DEFINE_INLINE_VIRTUAL_TRACE() {}
+  // Whether the layout node cannot produce any more fragments.
+  bool IsFinished() const { return is_finished_; }

[Gleb Lanbin, 2017/02/15 19:21:38]

.nit you used "exhausted" word to explain this case before. IsExhausted?

[ikilpatrick, 2017/02/16 17:01:30]

I'll keep as IsFinished, but reworded above...

+
+  // Returns the node associated with this break token. A break token cannot be
+  // used with any other node.
+  NGLayoutInputNode* InputNode() const { return node_.get(); }

[Gleb Lanbin, 2017/02/15 19:21:39]

just return node_;

[ikilpatrick, 2017/02/16 17:01:30]

Done.

+
+  DEFINE_INLINE_VIRTUAL_TRACE() { visitor->trace(node_); }
 
  protected:
-  NGBreakToken(NGBreakTokenType type) : type_(type) {}
+  NGBreakToken(NGBreakTokenType type, bool is_finished, NGLayoutInputNode* node)
+      : type_(type), is_finished_(is_finished), node_(node) {}
 
  private:
   unsigned type_ : 1;
+  unsigned is_finished_ : 1;
+
+  Member<NGLayoutInputNode> node_;
 };
 
 }  // namespace blink
 
 #endif  // NGBreakToken_h