Bug 1770877 - part 26: Make `HTMLEditor::InsertBRElementIfEmptyBlockElement` a lambda since it's used only by one method r=m_kato

And its selection update are not used except the legacy mutation event
listeners so that we can drop them.

Differential Revision: https://phabricator.services.mozilla.com/D149090

editor/libeditor/HTMLEditSubActionHandler.cpp

@@ -7452,12 +7452,38 @@ nsresult HTMLEditor::SplitParagraph(Element& aParentDivOrP,
   // it'll be exposed as <br> with Element.innerHTML.  Therefore, we can use
   // normal <br> elements for placeholder in this case.  Note that Chromium
   // also behaves so.
+  auto InsertBRElementIfEmptyBlockElement =
+      [&](Element& aElement) MOZ_CAN_RUN_SCRIPT {
+        if (!HTMLEditUtils::IsBlockElement(aElement)) {
+          return NS_OK;
+        }
+
+        if (!HTMLEditUtils::IsEmptyNode(
+                aElement, {EmptyCheckOption::TreatSingleBRElementAsVisible})) {
+          return NS_OK;
+        }
+
+        CreateElementResult insertBRElementResult = InsertBRElement(
+            WithTransaction::Yes, EditorDOMPoint(&aElement, 0u));
+        if (insertBRElementResult.isErr()) {
+          NS_WARNING(
+              "HTMLEditor::InsertBRElement(WithTransaction::Yes) failed");
+          return insertBRElementResult.unwrapErr();
+        }
+        // After this is called twice, selection will be updated by
+        // SplitParagraph itself.  Therefore, we don't need to update selection
+        // here.
+        insertBRElementResult.IgnoreCaretPointSuggestion();
+        return NS_OK;
+      };
+
   // MOZ_KnownLive(leftDivOrParagraphElement) because it's grabbed by
   // splitDivOrResult.
   rv = InsertBRElementIfEmptyBlockElement(
       MOZ_KnownLive(*leftDivOrParagraphElement));
   if (NS_FAILED(rv)) {
-    NS_WARNING("HTMLEditor::InsertBRElementIfEmptyBlockElement() failed");
+    NS_WARNING(
+        "InsertBRElementIfEmptyBlockElement(leftDivOrParagraphElement) failed");
     return rv;
   }
   // MOZ_KnownLive(rightDivOrParagraphElement) because it's grabbed by
@@ -7465,7 +7491,9 @@ nsresult HTMLEditor::SplitParagraph(Element& aParentDivOrP,
   rv = InsertBRElementIfEmptyBlockElement(
       MOZ_KnownLive(*rightDivOrParagraphElement));
   if (NS_FAILED(rv)) {
-    NS_WARNING("HTMLEditor::InsertBRElementIfEmptyBlockElement() failed");
+    NS_WARNING(
+        "InsertBRElementIfEmptyBlockElement(rightDivOrParagraphElement) "
+        "failed");
     return rv;
   }
 
@@ -9558,40 +9586,6 @@ nsresult HTMLEditor::InsertPaddingBRElementForEmptyLastLineIfNeeded(
   return NS_OK;
 }
 
-nsresult HTMLEditor::InsertBRElementIfEmptyBlockElement(Element& aElement) {
-  MOZ_ASSERT(IsEditActionDataAvailable());
-
-  if (!HTMLEditUtils::IsBlockElement(aElement)) {
-    return NS_OK;
-  }
-
-  if (!HTMLEditUtils::IsEmptyNode(
-          aElement, {EmptyCheckOption::TreatSingleBRElementAsVisible})) {
-    return NS_OK;
-  }
-
-  CreateElementResult insertBRElementResult =
-      InsertBRElement(WithTransaction::Yes, EditorDOMPoint(&aElement, 0u));
-  if (insertBRElementResult.isErr()) {
-    NS_WARNING("HTMLEditor::InsertBRElement(WithTransaction::Yes) failed");
-    return insertBRElementResult.unwrapErr();
-  }
-  // XXX Is this intentional selection change?
-  nsresult rv = insertBRElementResult.SuggestCaretPointTo(
-      *this, {SuggestCaret::OnlyIfHasSuggestion,
-              SuggestCaret::OnlyIfTransactionsAllowedToDoIt,
-              SuggestCaret::AndIgnoreTrivialError});
-  if (NS_FAILED(rv)) {
-    NS_WARNING("CreateElementResult::SuggestCaretPointTo() failed");
-    return rv;
-  }
-  NS_WARNING_ASSERTION(
-      rv != NS_SUCCESS_EDITOR_BUT_IGNORED_TRIVIAL_ERROR,
-      "CreateElementResult::SuggestCaretPointTo() failed, but ignored");
-  MOZ_ASSERT(insertBRElementResult.GetNewNode());
-  return NS_OK;
-}
-
 nsresult HTMLEditor::RemoveAlignFromDescendants(Element& aElement,
                                                 const nsAString& aAlignType,
                                                 EditTarget aEditTarget) {

editor/libeditor/HTMLEditor.h

@@ -1458,12 +1458,6 @@ class HTMLEditor final : public EditorBase,
   InsertBRElementIfHardLineIsEmptyAndEndsWithBlockBoundary(
       const EditorDOMPoint& aPointToInsert);
 
-  /**
-   * Insert a `<br>` element if aElement is a block element and empty.
-   */
-  [[nodiscard]] MOZ_CAN_RUN_SCRIPT nsresult
-  InsertBRElementIfEmptyBlockElement(Element& aElement);
-
   /**
    * Insert padding `<br>` element for empty last line into aElement if
    * aElement is a block element and empty.