Change NGLayoutOpportunityIterator constructor to work with const CS.

List of changes:
1) Resolve "const NGConstraintSpace" TODO in NGFloatingObject
2) Change NGLayoutOpportunityIterator to work with a const CS.

BUG=635619

Review-Url: https://codereview.chromium.org/2732483002
Cr-Commit-Position: refs/heads/master@{#454392}

third_party/WebKit/Source/core/layout/ng/ng_block_layout_algorithm.cc

@@ -134,7 +134,7 @@ NGLogicalOffset AdjustToTopEdgeAlignmentRule(const NGConstraintSpace& space,
 // @param margins Margins of the fragment.
 // @return Layout opportunity for the fragment.
 const NGLayoutOpportunity FindLayoutOpportunityForFragment(
-    NGConstraintSpace* space,
+    const NGConstraintSpace* space,
     const NGFragment& fragment,
     const NGLogicalOffset& origin_point,
     const NGBoxStrut& margins) {
@@ -186,8 +186,9 @@ NGLogicalOffset CalculateLogicalOffsetForOpportunity(
 // floating object that is requested to be positioned from {@code origin_point}.
 NGLogicalOffset PositionFloat(const NGLogicalOffset& origin_point,
                               const NGLogicalOffset& from_offset,
-                              NGFloatingObject* floating_object) {
-  NGConstraintSpace* float_space = floating_object->space.get();
+                              NGFloatingObject* floating_object,
+                              NGConstraintSpace* new_parent_space) {
+  const auto* float_space = floating_object->space.get();
   DCHECK(floating_object->fragment) << "Fragment cannot be null here";
 
   // TODO(ikilpatrick): The writing mode switching here looks wrong.
@@ -212,7 +213,7 @@ NGLogicalOffset PositionFloat(const NGLogicalOffset& origin_point,
   const NGExclusion exclusion = CreateExclusion(
       float_fragment, opportunity, float_offset, floating_object->margins,
       floating_object->exclusion_type);
-  float_space->AddExclusion(exclusion);
+  new_parent_space->AddExclusion(exclusion);
 
   return CalculateLogicalOffsetForOpportunity(opportunity, float_offset,
                                               from_offset, floating_object);
@@ -234,13 +235,13 @@ void UpdateFloatingObjectLeftOffset(
 // Positions pending floats stored on the fragment builder starting from
 // {@code origin_point_block_offset}.
 void PositionPendingFloats(const LayoutUnit origin_point_block_offset,
-                           const NGConstraintSpace& new_parent_space,
+                           NGConstraintSpace* new_parent_space,
                            NGFragmentBuilder* builder) {
   DCHECK(builder->BfcOffset()) << "Parent BFC offset should be known here";
   LayoutUnit bfc_block_offset = builder->BfcOffset().value().block_offset;
 
   for (auto& floating_object : builder->UnpositionedFloats()) {
-    NGConstraintSpace* float_space = floating_object->space.get();
+    const auto* float_space = floating_object->space.get();
     const NGConstraintSpace* original_parent_space =
         floating_object->original_parent_space.get();
 
@@ -249,10 +250,10 @@ void PositionPendingFloats(const LayoutUnit origin_point_block_offset,
     NGLogicalOffset from_offset = {
         original_parent_space->BfcOffset().inline_offset, bfc_block_offset};
 
-    NGLogicalOffset float_fragment_offset =
-        PositionFloat(origin_point, from_offset, floating_object);
+    NGLogicalOffset float_fragment_offset = PositionFloat(
+        origin_point, from_offset, floating_object, new_parent_space);
     builder->AddFloatingObject(floating_object, float_fragment_offset);
-    UpdateFloatingObjectLeftOffset(new_parent_space, floating_object,
+    UpdateFloatingObjectLeftOffset(*new_parent_space, floating_object,
                                    float_fragment_offset);
   }
   builder->MutableUnpositionedFloats().clear();
@@ -499,8 +500,8 @@ RefPtr<NGLayoutResult> NGBlockLayoutAlgorithm::Layout() {
   if (block_size) {
     curr_bfc_offset_.block_offset += curr_margin_strut_.Sum();
     UpdateFragmentBfcOffset(curr_bfc_offset_);
-    PositionPendingFloats(curr_bfc_offset_.block_offset, ConstraintSpace(),
-                          &builder_);
+    PositionPendingFloats(curr_bfc_offset_.block_offset,
+                          MutableConstraintSpace(), &builder_);
   }
 
   // Margins collapsing:
@@ -558,9 +559,8 @@ void NGBlockLayoutAlgorithm::FinishChildLayout(
   if (child->Type() == NGLayoutInputNode::kLegacyBlock &&
       toNGBlockNode(child)->Style().isFloating()) {
     NGFloatingObject* floating_object = new NGFloatingObject(
-        layout_result->PhysicalFragment().get(), child_space, constraint_space_,
-        toNGBlockNode(child), toNGBlockNode(child)->Style(),
-        curr_child_margins_);
+        child_space, constraint_space_, toNGBlockNode(child)->Style(),
+        curr_child_margins_, layout_result->PhysicalFragment().get());
     builder_.AddUnpositionedFloat(floating_object);
     // No need to postpone the positioning if we know the correct offset.
     if (builder_.BfcOffset()) {
@@ -569,7 +569,7 @@ void NGBlockLayoutAlgorithm::FinishChildLayout(
       // Example: <div style="margin-bottom: 20px"><float></div>
       //          <div style="margin-bottom: 30px"></div>
       origin_point.block_offset += curr_margin_strut_.Sum();
-      PositionPendingFloats(origin_point.block_offset, ConstraintSpace(),
+      PositionPendingFloats(origin_point.block_offset, MutableConstraintSpace(),
                             &builder_);
     }
     return;
@@ -600,8 +600,8 @@ void NGBlockLayoutAlgorithm::FinishChildLayout(
   }
   if (bfc_offset) {
     UpdateFragmentBfcOffset(curr_bfc_offset_);
-    PositionPendingFloats(curr_bfc_offset_.block_offset, ConstraintSpace(),
-                          &builder_);
+    PositionPendingFloats(curr_bfc_offset_.block_offset,
+                          MutableConstraintSpace(), &builder_);
   }
   NGLogicalOffset logical_offset = CalculateLogicalOffset(bfc_offset);
 
@@ -696,8 +696,8 @@ RefPtr<NGConstraintSpace> NGBlockLayoutAlgorithm::CreateConstraintSpaceForChild(
     // Margins collapsing: Inline block.
     curr_bfc_offset_.block_offset += curr_margin_strut_.Sum();
     UpdateFragmentBfcOffset(curr_bfc_offset_);
-    PositionPendingFloats(curr_bfc_offset_.block_offset, ConstraintSpace(),
-                          &builder_);
+    PositionPendingFloats(curr_bfc_offset_.block_offset,
+                          MutableConstraintSpace(), &builder_);
     curr_margin_strut_ = {};
 
     return space_builder_.ToConstraintSpace(
@@ -730,8 +730,8 @@ RefPtr<NGConstraintSpace> NGBlockLayoutAlgorithm::CreateConstraintSpaceForChild(
       curr_margin_strut_ = NGMarginStrut();
       curr_child_margins_.block_start = LayoutUnit();
     }
-    PositionPendingFloats(curr_bfc_offset_.block_offset, ConstraintSpace(),
-                          &builder_);
+    PositionPendingFloats(curr_bfc_offset_.block_offset,
+                          MutableConstraintSpace(), &builder_);
     WTF::Optional<LayoutUnit> clearance_offset =
         GetClearanceOffset(constraint_space_->Exclusions(), child_style);
     space_builder_.SetClearanceOffset(clearance_offset);

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

@@ -76,6 +76,9 @@ class CORE_EXPORT NGBlockLayoutAlgorithm : public NGLayoutAlgorithm {
 
   const ComputedStyle& Style() const { return node_->Style(); }
 
+  // Mutable Getters.
+  NGConstraintSpace* MutableConstraintSpace() { return constraint_space_; }
+
   Persistent<NGBlockNode> node_;
   NGConstraintSpace* constraint_space_;
 

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

@@ -19,35 +19,34 @@ class NGPhysicalFragment;
 // Struct that keeps all information needed to position floats in LayoutNG.
 struct CORE_EXPORT NGFloatingObject
     : public GarbageCollectedFinalized<NGFloatingObject> {
-  NGFloatingObject(NGPhysicalFragment* fragment,
-                   NGConstraintSpace* space,
+  NGFloatingObject(const NGConstraintSpace* space,
                    const NGConstraintSpace* parent_space,
-                   NGBlockNode* node,
                    const ComputedStyle& style,
-                   const NGBoxStrut& margins)
-      : fragment(fragment),
-        space(space),
+                   const NGBoxStrut& margins,
+                   NGPhysicalFragment* fragment)
+      : space(space),
         original_parent_space(parent_space),
-        node(node),
-        margins(margins) {
+        margins(margins),
+        fragment(fragment) {
     exclusion_type = NGExclusion::kFloatLeft;
     if (style.floating() == EFloat::kRight)
       exclusion_type = NGExclusion::kFloatRight;
     clear_type = style.clear();
   }
 
-  RefPtr<NGPhysicalFragment> fragment;
-  // TODO(glebl): Constraint space should be const here.
-  RefPtr<NGConstraintSpace> space;
+  // Original constraint space of the float.
+  RefPtr<const NGConstraintSpace> space;
 
   // Parent space is used so we can calculate the inline offset relative to
   // the original parent of this float.
   RefPtr<const NGConstraintSpace> original_parent_space;
-  Member<NGBlockNode> node;
+
   NGExclusion::Type exclusion_type;
   EClear clear_type;
   NGBoxStrut margins;
 
+  RefPtr<NGPhysicalFragment> fragment;
+
   // In the case where a legacy FloatingObject is attached to not its own
   // parent, e.g. a float surrounded by a bunch of nested empty divs,
   // NG float fragment's LeftOffset() cannot be used as legacy FloatingObject's
@@ -58,7 +57,6 @@ struct CORE_EXPORT NGFloatingObject
   LayoutUnit left_offset;
 
   DEFINE_INLINE_TRACE() {
-    visitor->trace(node);
   }
 };
 

third_party/WebKit/Source/core/layout/ng/ng_layout_opportunity_iterator.cc

@@ -232,7 +232,7 @@ NGExclusion ToLeaderExclusion(const NGLogicalOffset& origin_point,
 }  // namespace
 
 NGLayoutOpportunityIterator::NGLayoutOpportunityIterator(
-    NGConstraintSpace* space,
+    const NGConstraintSpace* space,
     const WTF::Optional<NGLogicalOffset>& opt_origin_point,
     const WTF::Optional<NGLogicalOffset>& opt_leader_point)
     : constraint_space_(space) {

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

@@ -33,7 +33,7 @@ class CORE_EXPORT NGLayoutOpportunityIterator final {
   //                         which starts from 'origin'. This rectangle may
   //                         represent a text fragment for example.
   NGLayoutOpportunityIterator(
-      NGConstraintSpace* space,
+      const NGConstraintSpace* space,
       const WTF::Optional<NGLogicalOffset>& opt_origin_point = WTF::nullopt,
       const WTF::Optional<NGLogicalOffset>& opt_leader_point = WTF::nullopt);
 
@@ -52,7 +52,7 @@ class CORE_EXPORT NGLayoutOpportunityIterator final {
     return opportunity_tree_root_.get();
   }
 
-  NGConstraintSpace* constraint_space_;
+  const NGConstraintSpace* constraint_space_;
 
   NGLayoutOpportunities opportunities_;
   NGLayoutOpportunities::const_iterator opportunity_iter_;