Use new downcast helper for LayoutTextControl & LayoutTextControlSingleLine

This CL has two goals to use new downcast helper for
blink::LayoutTextControl & blink::LayoutTextControlSingleLine.

Bug: 891908
Change-Id: I721ae55a1252a79b03575d5f2cd1c2a7ad3a0727
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2016697
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748119}

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

@@ -547,9 +547,9 @@ static Node* FindFirstMarkable(Node* node) {
       return nullptr;
     if (node->GetLayoutObject()->IsText())
       return node;
-    if (node->GetLayoutObject()->IsTextControl())
-      node = ToLayoutTextControl(node->GetLayoutObject())
-                 ->GetTextControlElement()
+    if (auto* text_control =
+            DynamicTo<LayoutTextControl>(node->GetLayoutObject()))
+      node = text_control->GetTextControlElement()
                  ->VisiblePositionForIndex(1)
                  .DeepEquivalent()
                  .AnchorNode();

third_party/blink/renderer/core/html/forms/text_field_input_type.cc

@@ -238,8 +238,8 @@ void TextFieldInputType::ForwardEvent(Event& event) {
        event.HasInterface(event_interface_names::kWheelEvent) ||
        event.type() == event_type_names::kBlur ||
        event.type() == event_type_names::kFocus)) {
-    LayoutTextControlSingleLine* layout_text_control =
-        ToLayoutTextControlSingleLine(GetElement().GetLayoutObject());
+    auto* layout_text_control =
+        To<LayoutTextControlSingleLine>(GetElement().GetLayoutObject());
     if (event.type() == event_type_names::kBlur) {
       if (LayoutBox* inner_editor_layout_object =
               GetElement().InnerEditorElement()->GetLayoutBox()) {

third_party/blink/renderer/core/input/keyboard_event_manager.cc

@@ -348,8 +348,8 @@ WebInputEventResult KeyboardEventManager::KeyEvent(
 void KeyboardEventManager::CapsLockStateMayHaveChanged() {
   if (Element* element = frame_->GetDocument()->FocusedElement()) {
     if (LayoutObject* r = element->GetLayoutObject()) {
-      if (r->IsTextField())
-        ToLayoutTextControlSingleLine(r)->CapsLockStateMayHaveChanged();
+      if (auto* text_control = DynamicTo<LayoutTextControlSingleLine>(r))
+        text_control->CapsLockStateMayHaveChanged();
     }
   }
 }

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

@@ -92,7 +92,12 @@ class CORE_EXPORT LayoutTextControl : public LayoutBlockFlow {
   bool CanBeProgramaticallyScrolled() const final { return true; }
 };
 
-DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutTextControl, IsTextControl());
+template <>
+struct DowncastTraits<LayoutTextControl> {
+  static bool AllowFrom(const LayoutObject& object) {
+    return object.IsTextControl();
+  }
+};
 
 }  // namespace blink
 

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

@@ -89,7 +89,12 @@ class LayoutTextControlSingleLine : public LayoutTextControl {
   bool should_draw_caps_lock_indicator_;
 };
 
-DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutTextControlSingleLine, IsTextField());
+template <>
+struct DowncastTraits<LayoutTextControlSingleLine> {
+  static bool AllowFrom(const LayoutObject& object) {
+    return object.IsTextField();
+  }
+};
 
 // ----------------------------
 

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

@@ -24,7 +24,7 @@ TEST_F(LayoutTextControlSingleLineTest, VisualOverflowCleared) {
     <input id=input type="text"></input.
   )HTML");
   auto* input =
-      ToLayoutTextControlSingleLine(GetLayoutObjectByElementId("input"));
+      To<LayoutTextControlSingleLine>(GetLayoutObjectByElementId("input"));
   if (::features::IsFormControlsRefreshEnabled()) {
     EXPECT_EQ(LayoutRect(-3, -3, 74, 72), input->SelfVisualOverflowRect());
   } else {

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

@@ -580,11 +580,11 @@ bool AXLayoutObject::IsPlaceholder() const {
     return false;
 
   LayoutObject* parent_layout_object = parent_object->GetLayoutObject();
-  if (!parent_layout_object || !parent_layout_object->IsTextControl())
+  auto* layout_text_control =
+      DynamicTo<LayoutTextControl>(parent_layout_object);
+  if (!layout_text_control)
     return false;
 
-  LayoutTextControl* layout_text_control =
-      ToLayoutTextControl(parent_layout_object);
   DCHECK(layout_text_control);
 
   TextControlElement* text_control_element =