[LayoutNG] Move instantiating the NGSimplifiedLayoutLayout into a method.

This was consuming an additional 160-bytes of stack.
Also makes NGBlockNode::RunLegacyLayout private.

Bug: 962034, 964926
Change-Id: I1e9f4b97d85b49d6262c07ae789bb984a66cc673
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1631126
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663938}

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

@@ -251,9 +251,7 @@ scoped_refptr<const NGLayoutResult> NGBlockNode::Layout(
     // may have gained or removed scrollbars, changing its size). In these
     // cases "simplified" layout will return a null layout-result, indicating
     // we need to perform a full layout.
-    layout_result =
-        NGSimplifiedLayoutAlgorithm(params, *box_->GetCachedLayoutResult())
-            .Layout();
+    layout_result = RunSimplifiedLayout(params);
 
 #if DCHECK_IS_ON()
     if (layout_result) {
@@ -1045,6 +1043,12 @@ scoped_refptr<const NGLayoutResult> NGBlockNode::RunLegacyLayout(
   return layout_result;
 }
 
+scoped_refptr<const NGLayoutResult> NGBlockNode::RunSimplifiedLayout(
+    const NGLayoutAlgorithmParams& params) const {
+  return NGSimplifiedLayoutAlgorithm(params, *box_->GetCachedLayoutResult())
+      .Layout();
+}
+
 void NGBlockNode::CopyBaselinesFromLegacyLayout(
     const NGConstraintSpace& constraint_space,
     NGBoxFragmentBuilder* builder) {

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

@@ -24,6 +24,7 @@ class NGPhysicalContainerFragment;
 class NGPhysicalFragment;
 struct MinMaxSize;
 struct NGBoxStrut;
+struct NGLayoutAlgorithmParams;
 struct LogicalOffset;
 
 // Represents a node to be laid out.
@@ -108,10 +109,6 @@ class CORE_EXPORT NGBlockNode final : public NGLayoutInputNode {
       FontBaseline,
       bool use_first_line_style);
 
-  // Runs layout on the underlying LayoutObject and creates a fragment for the
-  // resulting geometry.
-  scoped_refptr<const NGLayoutResult> RunLegacyLayout(const NGConstraintSpace&);
-
   // Called if this is an out-of-flow block which needs to be
   // positioned with legacy layout.
   void UseLegacyOutOfFlowPositioning() const;
@@ -131,6 +128,13 @@ class CORE_EXPORT NGBlockNode final : public NGLayoutInputNode {
  private:
   void PrepareForLayout();
 
+  // Runs layout on the underlying LayoutObject and creates a fragment for the
+  // resulting geometry.
+  scoped_refptr<const NGLayoutResult> RunLegacyLayout(const NGConstraintSpace&);
+
+  scoped_refptr<const NGLayoutResult> RunSimplifiedLayout(
+      const NGLayoutAlgorithmParams&) const;
+
   // If this node is a LayoutNGMixin, the caller must pass the layout object for
   // this node cast to a LayoutBlockFlow as the first argument.
   void FinishLayout(LayoutBlockFlow*,