Bug 1767386 - part 2: Make `HTMLEditor::RemoveInlinePropertyInternal` stop setting/removing style of an element if it's removed by `RemoveStyleInside` r=m_kato

`CSSEditUtils` will refer the composed document of the element to compute the
style of it.  However, it'll fail if `RemoveStyleInside` has already removed
the element from the DOM tree.  Therefore, `RemoveInlinePropertyInternal`
should stop handling the element immediately after calling `RemoveStyleInside`
if the element is removed.

Depends on D145303

Differential Revision: https://phabricator.services.mozilla.com/D145304

editor/libeditor/HTMLEditor.h

@@ -4075,6 +4075,8 @@ class HTMLEditor final : public EditorBase,
    * RemoveStyleInside() removes elements which represent aProperty/aAttribute
    * and removes CSS style.  This handles aElement and all its descendants
    * (including leaf text nodes) recursively.
+   * TODO: Rename this to explain that this maybe remove aElement from the DOM
+   *       tree.
    *
    * @param aSpecifiedStyle  Whether the class and style attributes should
    *                         be preserved or discareded.

editor/libeditor/HTMLStyleEditor.cpp

@@ -2156,6 +2156,11 @@ nsresult HTMLEditor::RemoveInlinePropertyInternal(
               NS_WARNING("HTMLEditor::RemoveStyleInside() failed");
               return rv;
             }
+            // If the element was removed from the DOM tree by
+            // RemoveStyleInside, we need nothing to do for it anymore.
+            if (!content->GetParentNode()) {
+              continue;
+            }
           }
 
           Result<bool, nsresult> isRemovableParentStyleOrError =
@@ -2222,6 +2227,8 @@ nsresult HTMLEditor::RemoveInlinePropertyInternal(
           // they still have the style.
           AutoTArray<OwningNonNull<Text>, 32> leafTextNodes;
           for (OwningNonNull<nsIContent>& content : arrayOfContents) {
+            // XXX Should we ignore content which has already removed from the
+            //     DOM tree by the previous for-loop?
             if (content->IsElement()) {
               CollectEditableLeafTextNodes(*content->AsElement(),
                                            leafTextNodes);