Bug 1500862 - part 2: Create AutoTransactionBatchExternal class which calls XPCOM methods instead of non-virtual internal methods r=m_kato

Unfortunately, TextServicesDocument::InsertText() is too complicated to
do it with both editor class and TextServicesDocument separately.
Therefore, this patch adds AutoTransactionBatchExternal class which is
almost same as AutoTransactionBatch but uses XPCOM methods to begin/end
transaction.  This change helps editor to manage whether it starts to
handle new edit action or not when BeginTransaction() is called explicitly.

Differential Revision: https://phabricator.services.mozilla.com/D9478

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

editor/libeditor/EditorUtils.h

@@ -451,6 +451,34 @@ private:
   SplitRangeOffFromNodeResult() = delete;
 };
 
+/***************************************************************************
+ * stack based helper class for calling EditorBase::EndTransaction() after
+ * EditorBase::BeginTransaction().  This shouldn't be used in editor classes
+ * or helper classes while an edit action is being handled.  Use
+ * AutoTransactionBatch in such cases since it uses non-virtual internal
+ * methods.
+ ***************************************************************************/
+class MOZ_RAII AutoTransactionBatchExternal final
+{
+private:
+  OwningNonNull<EditorBase> mEditorBase;
+  MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+
+public:
+  explicit AutoTransactionBatchExternal(EditorBase& aEditorBase
+                                        MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+    : mEditorBase(aEditorBase)
+  {
+    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+    mEditorBase->BeginTransaction();
+  }
+
+  ~AutoTransactionBatchExternal()
+  {
+    mEditorBase->EndTransaction();
+  }
+};
+
 /***************************************************************************
  * stack based helper class for calling EditorBase::EndTransaction() after
  * EditorBase::BeginTransaction().

editor/spellchecker/TextServicesDocument.cpp

@@ -1148,12 +1148,9 @@ TextServicesDocument::InsertText(const nsString* aText)
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
-  // AutoTransactionBatch grabs mTextEditor, so, we don't need to grab the
-  // instance with local variable here.
-  // XXX Well, do we really need to create AutoTransactionBatch here?
-  //     Looks like that after InsertTextAsAction(), this does nothing
-  //     from a point of view of editor.
-  AutoTransactionBatch bundleAllTransactions(*mTextEditor);
+  // AutoTransactionBatchExternal grabs mTextEditor, so, we don't need to grab
+  // the instance with local variable here.
+  AutoTransactionBatchExternal treatAsOneTransaction(*mTextEditor);
 
   nsresult rv = mTextEditor->InsertTextAsAction(*aText);
   if (NS_FAILED(rv)) {