[FlexNG] Update comment and make a member const

Just code health, no behavior change.

Bug: 845235
Change-Id: I1202f1c37751537e8112c33f3b1228647407b6dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1895748Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: David Grogan <dgrogan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712021}

third_party/blink/renderer/core/layout/ng/ng_flex_layout_algorithm.cc

@@ -26,7 +26,8 @@ NGFlexLayoutAlgorithm::NGFlexLayoutAlgorithm(
                       params.fragment_geometry.padding),
       border_scrollbar_padding_(border_padding_ +
                                 params.fragment_geometry.scrollbar),
-      is_column_(Style().ResolvedIsColumnFlexDirection()) {
+      is_column_(Style().ResolvedIsColumnFlexDirection()),
+      is_horizontal_flow_(FlexLayoutAlgorithm::IsHorizontalFlow(Style())) {
   container_builder_.SetIsNewFormattingContext(
       params.space.IsNewFormattingContext());
   container_builder_.SetInitialFragmentGeometry(params.fragment_geometry);
@@ -498,7 +499,6 @@ scoped_refptr<const NGLayoutResult> NGFlexLayoutAlgorithm::Layout() {
 
   const LayoutUnit line_break_length = MainAxisContentExtent(LayoutUnit::Max());
   algorithm_.emplace(&Style(), line_break_length);
-  is_horizontal_flow_ = algorithm_->IsHorizontalFlow();
 
   ConstructAndAppendFlexItems();
 

third_party/blink/renderer/core/layout/ng/ng_flex_layout_algorithm.h

@@ -68,12 +68,12 @@ class CORE_EXPORT NGFlexLayoutAlgorithm
   const NGBoxStrut border_padding_;
   const NGBoxStrut border_scrollbar_padding_;
   const bool is_column_;
-  LogicalSize border_box_size_;
-  LogicalSize content_box_size_;
+  const bool is_horizontal_flow_;
   // These are populated at the top of Layout(), so aren't available in
   // ComputeMinMaxSize() or anything it calls.
+  LogicalSize border_box_size_;
+  LogicalSize content_box_size_;
   base::Optional<FlexLayoutAlgorithm> algorithm_;
-  bool is_horizontal_flow_;
 };
 
 }  // namespace blink