[LayoutNG] Switch NGConstraintSpace to being RefCounted.

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.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 NGBlockLayoutAlgorithm_h
 #define NGBlockLayoutAlgorithm_h
 
 #include "core/CoreExport.h"
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_break_token.h"
@@ skipping 25 matching lines @@
                          NGBlockBreakToken* break_token = nullptr);
 
   Optional<MinAndMaxContentSizes> ComputeMinAndMaxContentSizes() const override;
   RefPtr<NGLayoutResult> Layout() override;
 
  private:
   NGBoxStrut CalculateMargins(NGBlockNode* child,
                               const NGConstraintSpace& space);
 
   // Creates a new constraint space for the current child.
-  NGConstraintSpace* CreateConstraintSpaceForChild(NGLayoutInputNode*);
+  RefPtr<NGConstraintSpace> CreateConstraintSpaceForChild(NGLayoutInputNode*);
   void FinishChildLayout(NGLayoutInputNode*,
                          NGConstraintSpace*,
                          RefPtr<NGLayoutResult>);
 
   // Layout inline children.
   void LayoutInlineChildren(NGInlineNode*, NGConstraintSpace*);
 
   // Final adjustments before fragment creation. We need to prevent the
   // fragment from crossing fragmentainer boundaries, and rather create a break
   // token if we're out of space.
   void FinalizeForFragmentation();
 
   // Calculates logical offset for the current fragment using either
   // {@code content_size_} when the fragment doesn't know it's offset
   // or {@code known_fragment_offset} if the fragment knows it's offset
   // @return Fragment's offset relative to the fragment's parent.
   NGLogicalOffset CalculateLogicalOffset(
       const WTF::Optional<NGLogicalOffset>& known_fragment_offset);
 
   // Updates the fragment's BFC offset if it's not already set.
   void UpdateFragmentBfcOffset(const NGLogicalOffset& offset);
 
   NGLogicalOffset GetChildSpaceOffset() const {
     return NGLogicalOffset(border_and_padding_.inline_start, content_size_);
   }
 
   const NGConstraintSpace& ConstraintSpace() const {
+    DCHECK(constraint_space_);
     return *constraint_space_;
   }
 
   const ComputedStyle& Style() const { return node_->Style(); }
 
   Persistent<NGBlockNode> node_;
-  Persistent<NGConstraintSpace> constraint_space_;
+  NGConstraintSpace* constraint_space_;

[ikilpatrick, 2017/03/02 17:20:15]

Just a pointer as STACK_ALLOCATED(). Going to change the BreakToken patch to
match this.

 
   // The break token from which we are currently resuming layout.
   Persistent<NGBlockBreakToken> break_token_;
 
   NGFragmentBuilder builder_;
   NGConstraintSpaceBuilder space_builder_;
 
   NGBoxStrut border_and_padding_;
   LayoutUnit content_size_;
   LayoutUnit max_inline_size_;
   // MarginStrut for the previous child.
   NGMarginStrut curr_margin_strut_;
   NGLogicalOffset curr_bfc_offset_;
   NGBoxStrut curr_child_margins_;
 };
 
 }  // namespace blink
 
 #endif  // NGBlockLayoutAlgorithm_h