Bug 771435 - Fix nsEditor::DoTransaction to use transaction interfaces sanely; r=ehsan

editor/libeditor/base/nsEditor.cpp

@@ -617,19 +617,7 @@ NS_IMETHODIMP
 nsEditor::DoTransaction(nsITransaction* aTxn)
 {
   if (mPlaceHolderBatch && !mPlaceHolderTxn) {
-    // it's pretty darn amazing how many different types of pointers this
-    // transaction goes through here.  I bet this is a record.
-
-    // We start off with an EditTxn since that's what the factory returns.
-    nsRefPtr<EditTxn> editTxn = new PlaceholderTxn();
-
-    // Then we QI to an nsIAbsorbingTransaction to get at placeholder
-    // functionality
-    nsCOMPtr<nsIAbsorbingTransaction> plcTxn;
-    editTxn->QueryInterface(NS_GET_IID(nsIAbsorbingTransaction),
-                            getter_AddRefs(plcTxn));
-    // have to use line above instead of "plcTxn = do_QueryInterface(editTxn);"
-    // due to our broken interface model for transactions.
+    nsCOMPtr<nsIAbsorbingTransaction> plcTxn = new PlaceholderTxn();
 
     // save off weak reference to placeholder txn
     mPlaceHolderTxn = do_GetWeakReference(plcTxn);
@@ -637,8 +625,7 @@ nsEditor::DoTransaction(nsITransaction* aTxn)
     // placeholder txn took ownership of this pointer
     mSelState = nsnull;
 
-    // finally we QI to an nsITransaction since that's what DoTransaction()
-    // expects
+    // QI to an nsITransaction since that's what DoTransaction() expects
     nsCOMPtr<nsITransaction> theTxn = do_QueryInterface(plcTxn);
     // we will recurse, but will not hit this case in the nested call
     DoTransaction(theTxn);