TextControl NG: Remove DowncastTraits<LayoutTextControl>

Text controls in LayoutNG won't inherit from LayoutTextControl. We
should avoid operations on LayoutTextControl.

All of usages of casting to LayoutTextControl were to get
TextControlElements. This CL replaces them with
To<TextControlElement>(layout_object->GetNode()).

This CL has no behavior changes.

Bug: 1040826
Change-Id: Ic6879147314e91cdaf361734e8d6a06300eaeb6f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2438097
Commit-Queue: Kent Tamura <tkent@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#812015}

third_party/blink/renderer/core/editing/spellcheck/spell_checker.cc

@@ -53,7 +53,7 @@
 #include "third_party/blink/renderer/core/html/forms/html_input_element.h"
 #include "third_party/blink/renderer/core/html_names.h"
 #include "third_party/blink/renderer/core/input_type_names.h"
-#include "third_party/blink/renderer/core/layout/layout_text_control.h"
+#include "third_party/blink/renderer/core/layout/layout_object.h"
 #include "third_party/blink/renderer/core/loader/empty_clients.h"
 #include "third_party/blink/renderer/core/page/page.h"
 #include "third_party/blink/renderer/platform/heap/heap.h"
@@ -551,20 +551,21 @@ void SpellChecker::RemoveSpellingMarkersUnderWords(
 
 static Node* FindFirstMarkable(Node* node) {
   while (node) {
-    if (!node->GetLayoutObject())
+    LayoutObject* layout_object = node->GetLayoutObject();
+    if (!layout_object)
       return nullptr;
-    if (node->GetLayoutObject()->IsText())
+    if (layout_object->IsText())
       return node;
-    if (auto* text_control =
-            DynamicTo<LayoutTextControl>(node->GetLayoutObject()))
-      node = text_control->GetTextControlElement()
+    if (layout_object->IsTextControl()) {
+      node = To<TextControlElement>(node)
                  ->VisiblePositionForIndex(1)
                  .DeepEquivalent()
                  .AnchorNode();
-    else if (node->hasChildren())
+    } else if (node->hasChildren()) {
       node = node->firstChild();
-    else
+    } else {
       node = node->nextSibling();
+    }
   }
 
   return nullptr;

third_party/blink/renderer/core/html/forms/text_control_element.h

@@ -269,6 +269,14 @@ DEFINE_TEXT_CONTROL_CASTS(const TextControlElement, const Node);
 
 #undef DEFINE_TEXT_CONTROL_CASTS
 
+template <>
+struct DowncastTraits<TextControlElement> {
+  static bool AllowFrom(const Node& node) {
+    return node.HasTagName(html_names::kInputTag) ||
+           node.HasTagName(html_names::kTextareaTag);
+  }
+};
+
 TextControlElement* EnclosingTextControl(const Position&);
 TextControlElement* EnclosingTextControl(const PositionInFlatTree&);
 TextControlElement* EnclosingTextControl(const Node*);

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

@@ -99,13 +99,6 @@ class CORE_EXPORT LayoutTextControl : public LayoutBlockFlow {
   }
 };
 
-template <>
-struct DowncastTraits<LayoutTextControl> {
-  static bool AllowFrom(const LayoutObject& object) {
-    return object.IsTextControl();
-  }
-};
-
 }  // namespace blink
 
 #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_LAYOUT_LAYOUT_TEXT_CONTROL_H_

third_party/blink/renderer/modules/accessibility/ax_layout_object.cc

@@ -71,7 +71,6 @@
 #include "third_party/blink/renderer/core/layout/layout_table_cell.h"
 #include "third_party/blink/renderer/core/layout/layout_table_row.h"
 #include "third_party/blink/renderer/core/layout/layout_table_section.h"
-#include "third_party/blink/renderer/core/layout/layout_text_control.h"
 #include "third_party/blink/renderer/core/layout/layout_text_fragment.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
 #include "third_party/blink/renderer/core/layout/list_marker.h"
@@ -592,18 +591,11 @@ bool AXLayoutObject::IsPlaceholder() const {
     return false;
 
   LayoutObject* parent_layout_object = parent_object->GetLayoutObject();
-  auto* layout_text_control =
-      DynamicTo<LayoutTextControl>(parent_layout_object);
-  if (!layout_text_control)
-    return false;
-
-  DCHECK(layout_text_control);
-
-  TextControlElement* text_control_element =
-      layout_text_control->GetTextControlElement();
-  if (!text_control_element)
+  if (!parent_layout_object || !parent_layout_object->IsTextControl())
     return false;
 
+  const auto* text_control_element =
+      To<TextControlElement>(parent_layout_object->GetNode());
   HTMLElement* placeholder_element = text_control_element->PlaceholderElement();
 
   return GetElement() == static_cast<Element*>(placeholder_element);