Bug 1599843 - Document::ChangeContentEditableCount is infallible. r=masayuki

And should take Element, not nsIContent pointers.

Depends on D54993

Differential Revision: https://phabricator.services.mozilla.com/D54994

--HG--
extra : moz-landing-system : lando

dom/base/Document.cpp

@@ -5299,7 +5299,7 @@ nsresult Document::EditingStateChanged() {
 // Helper class, used below in ChangeContentEditableCount().
 class DeferredContentEditableCountChangeEvent : public Runnable {
  public:
-  DeferredContentEditableCountChangeEvent(Document* aDoc, nsIContent* aElement)
+  DeferredContentEditableCountChangeEvent(Document* aDoc, Element* aElement)
       : mozilla::Runnable("DeferredContentEditableCountChangeEvent"),
         mDoc(aDoc),
         mElement(aElement) {}
@@ -5313,11 +5313,10 @@ class DeferredContentEditableCountChangeEvent : public Runnable {
 
  private:
   RefPtr<Document> mDoc;
-  nsCOMPtr<nsIContent> mElement;
+  RefPtr<Element> mElement;
 };
 
-nsresult Document::ChangeContentEditableCount(nsIContent* aElement,
-                                              int32_t aChange) {
+void Document::ChangeContentEditableCount(Element* aElement, int32_t aChange) {
   NS_ASSERTION(int32_t(mContentEditableCount) + aChange >= 0,
                "Trying to decrement too much.");
 
@@ -5325,11 +5324,9 @@ nsresult Document::ChangeContentEditableCount(nsIContent* aElement,
 
   nsContentUtils::AddScriptRunner(
       new DeferredContentEditableCountChangeEvent(this, aElement));
-
-  return NS_OK;
 }
 
-void Document::DeferredContentEditableCountChange(nsIContent* aElement) {
+void Document::DeferredContentEditableCountChange(Element* aElement) {
   if (mParser ||
       (mUpdateNestLevel > 0 && (mContentEditableCount > 0) != IsEditingOn())) {
     return;

dom/base/Document.h

@@ -1747,13 +1747,11 @@ class Document : public nsINode,
    * Should be called when an element's editable changes as a result of
    * changing its contentEditable attribute/property.
    *
-   * @param aElement the element for which the contentEditable
-   *                 attribute/property was changed
-   * @param aChange +1 if the contentEditable attribute/property was changed to
-   *                true, -1 if it was changed to false
+   * The change should be +1 if the contentEditable attribute/property was
+   * changed to true, -1 if it was changed to false.
    */
-  nsresult ChangeContentEditableCount(nsIContent* aElement, int32_t aChange);
-  void DeferredContentEditableCountChange(nsIContent* aElement);
+  void ChangeContentEditableCount(Element*, int32_t aChange);
+  void DeferredContentEditableCountChange(Element*);
 
   enum class EditingState : int8_t {
     eTearingDown = -2,