Use new downcast helper for blink::HTMLQuoteElement

This CL has two goals,
  1. Use To<HTMLQuoteElement> and DynamicTo<HTMLQuoteElement> as new
   downcast helper
  2. Use IsA<HTMLQuoteElement>(element) in place of
   IsHTMLQuoteElement(element)

Bug: 891908
Change-Id: Ie3908bdfd769857c8bc6332a5fbd794bc13b6884
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930544Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: Abhijeet | Igalia <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#719504}

third_party/blink/renderer/core/editing/commands/break_blockquote_command.cc

@@ -83,7 +83,7 @@ static HTMLQuoteElement* TopBlockquoteOf(const Position& start) {
   // |position| will be in the first node that we need to move (there are a few
   // exceptions to this, see |doApply|).
   const Position& position = MostForwardCaretPosition(start);
-  return ToHTMLQuoteElement(
+  return To<HTMLQuoteElement>(
       HighestEnclosingNodeOfType(position, IsMailHTMLBlockquoteElement));
 }
 
@@ -172,7 +172,7 @@ void BreakBlockquoteCommand::DoApply(EditingState* editing_state) {
 
   // Adjust the position so we don't split at the beginning of a quote.
   while (IsFirstVisiblePositionInNode(CreateVisiblePosition(pos),
-                                      ToHTMLQuoteElement(EnclosingNodeOfType(
+                                      To<HTMLQuoteElement>(EnclosingNodeOfType(
                                           pos, IsMailHTMLBlockquoteElement)))) {
     pos = PreviousPositionOf(pos, PositionMoveType::kGraphemeCluster);
   }

third_party/blink/renderer/core/editing/commands/composite_edit_command.cc

@@ -1772,9 +1772,8 @@ bool CompositeEditCommand::BreakOutOfEmptyMailBlockquotedParagraph(
   GetDocument().UpdateStyleAndLayout();
 
   VisiblePosition caret = EndingVisibleSelection().VisibleStart();
-  HTMLQuoteElement* highest_blockquote =
-      ToHTMLQuoteElement(HighestEnclosingNodeOfType(
-          caret.DeepEquivalent(), &IsMailHTMLBlockquoteElement));
+  auto* highest_blockquote = To<HTMLQuoteElement>(HighestEnclosingNodeOfType(
+      caret.DeepEquivalent(), &IsMailHTMLBlockquoteElement));
   if (!highest_blockquote)
     return false;
 

third_party/blink/renderer/core/editing/commands/insert_paragraph_separator_command.cc

@@ -305,8 +305,8 @@ void InsertParagraphSeparatorCommand::DoApply(EditingState* editing_state) {
       // then don't want the newline within the blockquote or else it will also
       // be quoted.
       if (paste_blockquote_into_unquoted_area_) {
-        if (HTMLQuoteElement* highest_blockquote =
-                ToHTMLQuoteElement(HighestEnclosingNodeOfType(
+        if (auto* highest_blockquote =
+                To<HTMLQuoteElement>(HighestEnclosingNodeOfType(
                     canonical_pos, &IsMailHTMLBlockquoteElement)))
           start_block = highest_blockquote;
       }

third_party/blink/renderer/core/editing/commands/replace_selection_command.cc

@@ -598,10 +598,10 @@ void ReplaceSelectionCommand::RemoveRedundantStylesAndKeepStyleSpanInline(
       // you're pasting into a quoted region, styles from blockquoteNode are
       // allowed to override those from the source document, see
       // <rdar://problem/4930986> and <rdar://problem/5089327>.
-      HTMLQuoteElement* blockquote_element =
+      auto* blockquote_element =
           !context
-              ? ToHTMLQuoteElement(context)
-              : ToHTMLQuoteElement(EnclosingNodeOfType(
+              ? To<HTMLQuoteElement>(context)
+              : To<HTMLQuoteElement>(EnclosingNodeOfType(
                     Position::FirstPositionInNode(*context),
                     IsMailHTMLBlockquoteElement, kCanCrossEditingBoundary));
 

third_party/blink/renderer/core/editing/serializers/serialization.cc

@@ -207,8 +207,8 @@ static HTMLElement* HighestAncestorToWrapMarkup(
 
       // Retain the Mail quote level by including all ancestor mail block
       // quotes.
-      if (HTMLQuoteElement* highest_mail_blockquote =
-              ToHTMLQuoteElement(HighestEnclosingNodeOfType(
+      if (auto* highest_mail_blockquote =
+              To<HTMLQuoteElement>(HighestEnclosingNodeOfType(
                   first_node_position, IsMailHTMLBlockquoteElement,
                   kCanCrossEditingBoundary))) {
         special_common_ancestor = highest_mail_blockquote;

third_party/blink/renderer/core/html/html_quote_element.h

@@ -46,7 +46,25 @@ inline bool IsHTMLQuoteElement(const HTMLElement& element) {
          element.HasTagName(html_names::kBlockquoteTag);
 }
 
-DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLQuoteElement);
+template <>
+struct DowncastTraits<HTMLQuoteElement> {
+  static bool AllowFrom(const HTMLElement& element) {
+    return IsHTMLQuoteElement(element);
+  }
+  static bool AllowFrom(const HTMLElement* element) {
+    return element && IsHTMLQuoteElement(*element);
+  }
+  static bool AllowFrom(const Node& node) {
+    auto* html_element = DynamicTo<HTMLElement>(node);
+    return html_element ? IsHTMLQuoteElement(*html_element) : false;
+  }
+  static bool AllowFrom(const Node* node) {
+    return node && IsA<HTMLQuoteElement>(*node);
+  }
+  static bool AllowFrom(const Element* element) {
+    return element && IsA<HTMLQuoteElement>(*element);
+  }
+};
 
 }  // namespace blink