Remove unwanted ToElementOrNull and use To<Element> in place of ToElementOrDie

This CL removes the unused definition of ToElementOrNull as all the
occurrences of ToElementOrNull() is already replaced with
DynamicTo<Element>.

This CL uses To<Element> and CHECK() in place of ToElementOrDie() and
removes subsequent definition of ToElementOrDie().

Bug: 891908
Change-Id: I41328a58a8540aa1a981ed3f5609585e92865001
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1692761Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#676545}

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

@@ -1224,47 +1224,6 @@ inline const T* ToElement(const Node* node) {
   return static_cast<const T*>(node);
 }
 
-template <typename T>
-inline T* ToElementOrNull(Node& node) {
-  return IsElementOfType<const T>(node) ? static_cast<T*>(&node) : nullptr;
-}
-template <typename T>
-inline T* ToElementOrNull(Node* node) {
-  return (node && IsElementOfType<const T>(*node)) ? static_cast<T*>(node)
-                                                   : nullptr;
-}
-template <typename T>
-inline const T* ToElementOrNull(const Node& node) {
-  return IsElementOfType<const T>(node) ? static_cast<const T*>(&node)
-                                        : nullptr;
-}
-template <typename T>
-inline const T* ToElementOrNull(const Node* node) {
-  return (node && IsElementOfType<const T>(*node)) ? static_cast<const T*>(node)
-                                                   : nullptr;
-}
-
-template <typename T>
-inline T& ToElementOrDie(Node& node) {
-  CHECK(IsElementOfType<const T>(node));
-  return static_cast<T&>(node);
-}
-template <typename T>
-inline T* ToElementOrDie(Node* node) {
-  CHECK(!node || IsElementOfType<const T>(*node));
-  return static_cast<T*>(node);
-}
-template <typename T>
-inline const T& ToElementOrDie(const Node& node) {
-  CHECK(IsElementOfType<const T>(node));
-  return static_cast<const T&>(node);
-}
-template <typename T>
-inline const T* ToElementOrDie(const Node* node) {
-  CHECK(!node || IsElementOfType<const T>(*node));
-  return static_cast<const T*>(node);
-}
-
 inline bool IsDisabledFormControl(const Node* node) {
   auto* element = DynamicTo<Element>(node);
   return element && element->IsDisabledFormControl();

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

@@ -548,8 +548,8 @@ void DateTimeEditElement::Trace(Visitor* visitor) {
 }
 
 inline Element* DateTimeEditElement::FieldsWrapperElement() const {
-  DCHECK(firstChild());
-  return ToElementOrDie(firstChild());
+  CHECK(!firstChild() || IsA<Element>(firstChild()));
+  return To<Element>(firstChild());
 }
 
 void DateTimeEditElement::AddField(DateTimeFieldElement* field) {

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

@@ -323,16 +323,20 @@ void FileInputType::CreateShadowSubtree() {
 
 void FileInputType::DisabledAttributeChanged() {
   DCHECK(IsShadowHost(GetElement()));
+  CHECK(!GetElement().UserAgentShadowRoot()->firstChild() ||
+        IsA<Element>(GetElement().UserAgentShadowRoot()->firstChild()));
   if (Element* button =
-          ToElementOrDie(GetElement().UserAgentShadowRoot()->firstChild()))
+          To<Element>(GetElement().UserAgentShadowRoot()->firstChild()))
     button->SetBooleanAttribute(kDisabledAttr,
                                 GetElement().IsDisabledFormControl());
 }
 
 void FileInputType::MultipleAttributeChanged() {
   DCHECK(IsShadowHost(GetElement()));
+  CHECK(!GetElement().UserAgentShadowRoot()->firstChild() ||
+        IsA<Element>(GetElement().UserAgentShadowRoot()->firstChild()));
   if (Element* button =
-          ToElementOrDie(GetElement().UserAgentShadowRoot()->firstChild()))
+          To<Element>(GetElement().UserAgentShadowRoot()->firstChild()))
     button->setAttribute(
         kValueAttr,
         AtomicString(GetLocale().QueryString(