Remove ComputedStyle ref/deref within LayoutTreeBuilder.

As the LayoutTreeBuilder is only allowed to be stack-allocated, and
doesn't take direct ownership of the ComputedStyle, we can just store a
pointer to the ComputedStyle, instead of a scoped_refptr.

There should be no behaviour change.

Change-Id: Id70a0df625831aaf516b5b2c11537d9fd38498f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1638617Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665308}

third_party/blink/renderer/core/dom/layout_tree_builder.cc

@@ -47,7 +47,7 @@ namespace blink {
 
 LayoutTreeBuilderForElement::LayoutTreeBuilderForElement(Element& element,
                                                          ComputedStyle* style)
-    : LayoutTreeBuilder(element, nullptr), style_(style) {
+    : LayoutTreeBuilder(element, nullptr, style) {
   DCHECK(element.CanParticipateInFlatTree());
   DCHECK(style_);
   DCHECK(!style_->IsEnsuredInDisplayNone());

third_party/blink/renderer/core/dom/layout_tree_builder.h

@@ -59,8 +59,12 @@ class LayoutTreeBuilder {
   STACK_ALLOCATED();
 
  protected:
-  LayoutTreeBuilder(NodeType& node, LayoutObject* layout_object_parent)
-      : node_(node), layout_object_parent_(layout_object_parent) {
+  LayoutTreeBuilder(NodeType& node,
+                    LayoutObject* layout_object_parent,
+                    ComputedStyle* style)
+      : node_(node),
+        layout_object_parent_(layout_object_parent),
+        style_(style) {
     DCHECK(!node.GetLayoutObject());
     DCHECK(node.GetDocument().InStyleRecalc());
     DCHECK(node.InActiveDocument());
@@ -92,6 +96,7 @@ class LayoutTreeBuilder {
 
   Member<NodeType> node_;
   LayoutObject* layout_object_parent_;
+  ComputedStyle* style_;
 };
 
 class LayoutTreeBuilderForElement : public LayoutTreeBuilder<Element> {
@@ -108,8 +113,6 @@ class LayoutTreeBuilderForElement : public LayoutTreeBuilder<Element> {
   LayoutObject* NextLayoutObject() const;
   bool ShouldCreateLayoutObject() const;
   void CreateLayoutObject(LegacyLayout);
-
-  scoped_refptr<ComputedStyle> style_;
 };
 
 class LayoutTreeBuilderForText : public LayoutTreeBuilder<Text> {
@@ -117,14 +120,12 @@ class LayoutTreeBuilderForText : public LayoutTreeBuilder<Text> {
   LayoutTreeBuilderForText(Text& text,
                            LayoutObject* layout_parent,
                            ComputedStyle* style_from_parent)
-      : LayoutTreeBuilder(text, layout_parent), style_(style_from_parent) {}
+      : LayoutTreeBuilder(text, layout_parent, style_from_parent) {}
 
   void CreateLayoutObject();
 
  private:
   LayoutObject* CreateInlineWrapperForDisplayContentsIfNeeded();
-
-  scoped_refptr<ComputedStyle> style_;
 };
 
 }  // namespace blink