Centralize decision on whether to create an NG LayoutObject or not.

Introduces LayoutObjectFactory, which will be used more extensively in
follow-up CLs, so that nobody creates a LayoutBlockFlow on their own,
for instance.

Change-Id: Ib9124a6f02ee1e5f1213b1b61f18e0494d7bd268
Reviewed-on: https://chromium-review.googlesource.com/1095103
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566804}

third_party/blink/renderer/core/layout/BUILD.gn

@@ -170,6 +170,8 @@ blink_core_sources("layout") {
     "layout_object.h",
     "layout_object_child_list.cc",
     "layout_object_child_list.h",
+    "layout_object_factory.cc",
+    "layout_object_factory.h",
     "layout_object_inlines.h",
     "layout_paged_flow_thread.cc",
     "layout_paged_flow_thread.h",

third_party/blink/renderer/core/layout/layout_block_flow.cc

@@ -45,6 +45,7 @@
 #include "third_party/blink/renderer/core/layout/layout_inline.h"
 #include "third_party/blink/renderer/core/layout/layout_multi_column_flow_thread.h"
 #include "third_party/blink/renderer/core/layout/layout_multi_column_spanner_placeholder.h"
+#include "third_party/blink/renderer/core/layout/layout_object_factory.h"
 #include "third_party/blink/renderer/core/layout/layout_paged_flow_thread.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
 #include "third_party/blink/renderer/core/layout/line/glyph_overflow.h"
@@ -276,9 +277,7 @@ LayoutBlockFlow* LayoutBlockFlow::CreateAnonymous(
     Document* document,
     scoped_refptr<ComputedStyle> style) {
   LayoutBlockFlow* layout_block_flow =
-      RuntimeEnabledFeatures::LayoutNGEnabled() && !style->ForceLegacyLayout()
-          ? new LayoutNGBlockFlow(nullptr)
-          : new LayoutBlockFlow(nullptr);
+      LayoutObjectFactory::CreateBlockFlow(*document, *style);
   layout_block_flow->SetDocumentForAnonymous(document);
   layout_block_flow->SetStyle(style);
   return layout_block_flow;

third_party/blink/renderer/core/layout/layout_object.cc

@@ -70,6 +70,7 @@
 #include "third_party/blink/renderer/core/layout/layout_inline.h"
 #include "third_party/blink/renderer/core/layout/layout_list_item.h"
 #include "third_party/blink/renderer/core/layout/layout_multi_column_spanner_placeholder.h"
+#include "third_party/blink/renderer/core/layout/layout_object_factory.h"
 #include "third_party/blink/renderer/core/layout/layout_scrollbar_part.h"
 #include "third_party/blink/renderer/core/layout/layout_table_caption.h"
 #include "third_party/blink/renderer/core/layout/layout_table_cell.h"
@@ -79,11 +80,6 @@
 #include "third_party/blink/renderer/core/layout/layout_theme.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
 #include "third_party/blink/renderer/core/layout/ng/layout_ng_block_flow.h"
-#include "third_party/blink/renderer/core/layout/ng/layout_ng_flexible_box.h"
-#include "third_party/blink/renderer/core/layout/ng/layout_ng_table_caption.h"
-#include "third_party/blink/renderer/core/layout/ng/layout_ng_table_cell.h"
-#include "third_party/blink/renderer/core/layout/ng/list/layout_ng_list_item.h"
-#include "third_party/blink/renderer/core/layout/ng/list/layout_ng_list_marker.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_block_node.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_layout_result.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_unpositioned_float.h"
@@ -116,21 +112,6 @@ namespace blink {
 
 namespace {
 
-inline bool ShouldUseNewLayout(const Element& element,
-                               const ComputedStyle& style) {
-  if (!RuntimeEnabledFeatures::LayoutNGEnabled())
-    return false;
-  const Document& document = element.GetDocument();
-  bool requires_ng_block_fragmentation =
-      document.Printing() ||
-      (document.GetLayoutView() &&
-       document.GetLayoutView()->StyleRef().IsOverflowPaged());
-  if (requires_ng_block_fragmentation &&
-      !RuntimeEnabledFeatures::LayoutNGBlockFragmentationEnabled())
-    return false;
-  return !style.ForceLegacyLayout();
-}
-
 template <typename Predicate>
 LayoutObject* FindAncestorByPredicate(const LayoutObject* descendant,
                                       LayoutObject::AncestorSkipInfo* skip_info,
@@ -255,13 +236,9 @@ LayoutObject* LayoutObject::CreateObject(Element* element,
     case EDisplay::kBlock:
     case EDisplay::kFlowRoot:
     case EDisplay::kInlineBlock:
-      if (ShouldUseNewLayout(*element, style))
-        return new LayoutNGBlockFlow(element);
-      return new LayoutBlockFlow(element);
+      return LayoutObjectFactory::CreateBlockFlow(*element, style);
     case EDisplay::kListItem:
-      if (ShouldUseNewLayout(*element, style))
-        return new LayoutNGListItem(element);
-      return new LayoutListItem(element);
+      return LayoutObjectFactory::CreateListItem(*element, style);
     case EDisplay::kTable:
     case EDisplay::kInlineTable:
       return new LayoutTable(element);
@@ -275,23 +252,15 @@ LayoutObject* LayoutObject::CreateObject(Element* element,
     case EDisplay::kTableColumn:
       return new LayoutTableCol(element);
     case EDisplay::kTableCell:
-      if (ShouldUseNewLayout(*element, style))
-        return new LayoutNGTableCell(element);
-      return new LayoutTableCell(element);
+      return LayoutObjectFactory::CreateTableCell(*element, style);
     case EDisplay::kTableCaption:
-      if (ShouldUseNewLayout(*element, style))
-        return new LayoutNGTableCaption(element);
-      return new LayoutTableCaption(element);
+      return LayoutObjectFactory::CreateTableCaption(*element, style);
     case EDisplay::kWebkitBox:
     case EDisplay::kWebkitInlineBox:
       return new LayoutDeprecatedFlexibleBox(*element);
     case EDisplay::kFlex:
     case EDisplay::kInlineFlex:
-      if (RuntimeEnabledFeatures::LayoutNGFlexBoxEnabled() &&
-          ShouldUseNewLayout(*element, style)) {
-        return new LayoutNGFlexibleBox(element);
-      }
-      return new LayoutFlexibleBox(element);
+      return LayoutObjectFactory::CreateFlexibleBox(*element, style);
     case EDisplay::kGrid:
     case EDisplay::kInlineGrid:
       return new LayoutGrid(element);

third_party/blink/renderer/core/layout/layout_object_factory.cc

+// Copyright 2018 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.
+
+#include "third_party/blink/renderer/core/layout/layout_object_factory.h"
+
+#include "third_party/blink/renderer/core/dom/element.h"
+#include "third_party/blink/renderer/core/layout/layout_block_flow.h"
+#include "third_party/blink/renderer/core/layout/layout_flexible_box.h"
+#include "third_party/blink/renderer/core/layout/layout_list_item.h"
+#include "third_party/blink/renderer/core/layout/layout_table_caption.h"
+#include "third_party/blink/renderer/core/layout/layout_table_cell.h"
+#include "third_party/blink/renderer/core/layout/layout_view.h"
+#include "third_party/blink/renderer/core/layout/ng/layout_ng_block_flow.h"
+#include "third_party/blink/renderer/core/layout/ng/layout_ng_flexible_box.h"
+#include "third_party/blink/renderer/core/layout/ng/layout_ng_table_caption.h"
+#include "third_party/blink/renderer/core/layout/ng/layout_ng_table_cell.h"
+#include "third_party/blink/renderer/core/layout/ng/list/layout_ng_list_item.h"
+#include "third_party/blink/renderer/core/style/computed_style.h"
+#include "third_party/blink/renderer/platform/runtime_enabled_features.h"
+
+namespace blink {
+
+namespace {
+
+inline bool ShouldUseNewLayout(Document& document, const ComputedStyle& style) {
+  if (!RuntimeEnabledFeatures::LayoutNGEnabled())
+    return false;
+  bool requires_ng_block_fragmentation =
+      document.Printing() ||
+      (document.GetLayoutView() &&
+       document.GetLayoutView()->StyleRef().IsOverflowPaged());
+  if (requires_ng_block_fragmentation &&
+      !RuntimeEnabledFeatures::LayoutNGBlockFragmentationEnabled())
+    return false;
+  return !style.ForceLegacyLayout();
+}
+
+inline Element* GetElementForLayoutObject(Node& node) {
+  if (node.IsElementNode())
+    return &ToElement(node);
+  // If |node| is a Document, the layout object is going to be anonymous.
+  DCHECK(node.IsDocumentNode());
+  return nullptr;
+}
+
+}  // anonymous namespace
+
+LayoutBlockFlow* LayoutObjectFactory::CreateBlockFlow(
+    Node& node,
+    const ComputedStyle& style) {
+  Element* element = GetElementForLayoutObject(node);
+  if (ShouldUseNewLayout(node.GetDocument(), style))
+    return new LayoutNGBlockFlow(element);
+  return new LayoutBlockFlow(element);
+}
+
+LayoutBlock* LayoutObjectFactory::CreateFlexibleBox(
+    Node& node,
+    const ComputedStyle& style) {
+  Element* element = GetElementForLayoutObject(node);
+  if (RuntimeEnabledFeatures::LayoutNGFlexBoxEnabled() &&
+      ShouldUseNewLayout(node.GetDocument(), style))
+    return new LayoutNGFlexibleBox(element);
+  return new LayoutFlexibleBox(element);
+}
+
+LayoutBlockFlow* LayoutObjectFactory::CreateListItem(
+    Node& node,
+    const ComputedStyle& style) {
+  Element* element = GetElementForLayoutObject(node);
+  if (ShouldUseNewLayout(node.GetDocument(), style))
+    return new LayoutNGListItem(element);
+  return new LayoutListItem(element);
+}
+
+LayoutTableCaption* LayoutObjectFactory::CreateTableCaption(
+    Node& node,
+    const ComputedStyle& style) {
+  Element* element = GetElementForLayoutObject(node);
+  if (ShouldUseNewLayout(node.GetDocument(), style))
+    return new LayoutNGTableCaption(element);
+  return new LayoutTableCaption(element);
+}
+
+LayoutTableCell* LayoutObjectFactory::CreateTableCell(
+    Node& node,
+    const ComputedStyle& style) {
+  Element* element = GetElementForLayoutObject(node);
+  if (ShouldUseNewLayout(node.GetDocument(), style))
+    return new LayoutNGTableCell(element);
+  return new LayoutTableCell(element);
+}
+
+}  // namespace blink

third_party/blink/renderer/core/layout/layout_object_factory.h

+// Copyright 2018 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 THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_OBJECT_FACTORY_H_
+#define THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_OBJECT_FACTORY_H_
+
+#include "third_party/blink/renderer/core/layout/layout_object.h"
+#include "third_party/blink/renderer/platform/wtf/allocator.h"
+
+namespace blink {
+
+class LayoutBlock;
+class LayoutBlockFlow;
+class LayoutTableCaption;
+class LayoutTableCell;
+
+// Helper class for creation of certain LayoutObject-derived objects that may
+// need to be of different types, depending on whether or not LayoutNG is to be
+// used in the given context.
+class LayoutObjectFactory {
+  STATIC_ONLY(LayoutObjectFactory);
+
+ public:
+  // The following methods will create and return some LayoutObject-derived
+  // object. If |node| is of type Element, it will be associated with the new
+  // LayoutObject. Otherwise it will be assumed to be a Document node, in which
+  // case the LayoutObject created will be anonymous. The |style| reference
+  // passed will only be used to determine which object type to create.
+  static LayoutBlockFlow* CreateBlockFlow(Node&, const ComputedStyle&);
+  static LayoutBlock* CreateFlexibleBox(Node&, const ComputedStyle&);
+  static LayoutBlockFlow* CreateListItem(Node&, const ComputedStyle&);
+  static LayoutTableCaption* CreateTableCaption(Node&, const ComputedStyle&);
+  static LayoutTableCell* CreateTableCell(Node&, const ComputedStyle&);
+};
+
+}  // namespace blink
+
+#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_OBJECT_FACTORY_H_