Bug 1425412 - part 8: Create JoinNodeTransaction::MaybeCreate() and remove EditorBase::CreateTxnForJoinNode() r=m_kato

EditorBase::CreateTxnForJoinNode() just hides what it does.
For making the caller clearer, let's create a factory method,
JoinNodeTransaction::MaybeCreate().

MozReview-Commit-ID: 8vADXdzMeuV

--HG--
extra : rebase_source : 6a281aff11bfa019c292d26cadd0cd29da12753f

editor/libeditor/EditorBase.cpp

@@ -1634,11 +1634,13 @@ EditorBase::JoinNodes(nsINode& aLeftNode,
 
   nsresult rv = NS_OK;
   RefPtr<JoinNodeTransaction> transaction =
-    CreateTxnForJoinNode(aLeftNode, aRightNode);
+    JoinNodeTransaction::MaybeCreate(*this, aLeftNode, aRightNode);
   if (transaction)  {
     rv = DoTransaction(transaction);
   }
 
+  // XXX Some other transactions manage range updater by themselves.
+  //     Why doesn't JoinNodeTransaction do it?
   mRangeUpdater.SelAdjJoinNodes(aLeftNode, aRightNode, *parent, offset,
                                 (int32_t)oldLeftNodeLen);
 
@@ -3045,20 +3047,6 @@ EditorBase::DeleteText(nsGenericDOMDataNode& aCharData,
   return rv;
 }
 
-already_AddRefed<JoinNodeTransaction>
-EditorBase::CreateTxnForJoinNode(nsINode& aLeftNode,
-                                 nsINode& aRightNode)
-{
-  RefPtr<JoinNodeTransaction> joinNodeTransaction =
-    new JoinNodeTransaction(*this, aLeftNode, aRightNode);
-  // If it's not editable, the transaction shouldn't be recorded since it
-  // should never be undone/redone.
-  if (NS_WARN_IF(!joinNodeTransaction->CanDoIt())) {
-    return nullptr;
-  }
-  return joinNodeTransaction.forget();
-}
-
 struct SavedRange final
 {
   RefPtr<Selection> mSelection;

editor/libeditor/EditorBase.h

@@ -590,9 +590,6 @@ protected:
   nsresult DeleteText(nsGenericDOMDataNode& aElement,
                       uint32_t aOffset, uint32_t aLength);
 
-  already_AddRefed<JoinNodeTransaction>
-    CreateTxnForJoinNode(nsINode& aLeftNode, nsINode& aRightNode);
-
   /**
    * This method first deletes the selection, if it's not collapsed.  Then if
    * the selection lies in a CharacterData node, it splits it.  If the

editor/libeditor/JoinNodeTransaction.cpp

@@ -18,6 +18,20 @@ namespace mozilla {
 
 using namespace dom;
 
+// static
+already_AddRefed<JoinNodeTransaction>
+JoinNodeTransaction::MaybeCreate(EditorBase& aEditorBase,
+                                 nsINode& aLeftNode,
+                                 nsINode& aRightNode)
+{
+  RefPtr<JoinNodeTransaction> transaction =
+    new JoinNodeTransaction(aEditorBase, aLeftNode, aRightNode);
+  if (NS_WARN_IF(!transaction->CanDoIt())) {
+    return nullptr;
+  }
+  return transaction.forget();
+}
+
 JoinNodeTransaction::JoinNodeTransaction(EditorBase& aEditorBase,
                                          nsINode& aLeftNode,
                                          nsINode& aRightNode)

editor/libeditor/JoinNodeTransaction.h

@@ -26,14 +26,21 @@ class EditorBase;
  */
 class JoinNodeTransaction final : public EditTransactionBase
 {
+protected:
+  JoinNodeTransaction(EditorBase& aEditorBase,
+                      nsINode& aLeftNode, nsINode& aRightNode);
+
 public:
   /**
+   * Creates a join node transaction.  This returns nullptr if cannot join the
+   * nodes.
+   *
    * @param aEditorBase     The provider of core editing operations.
    * @param aLeftNode       The first of two nodes to join.
    * @param aRightNode      The second of two nodes to join.
    */
-  JoinNodeTransaction(EditorBase& aEditorBase,
-                      nsINode& aLeftNode, nsINode& aRightNode);
+  static already_AddRefed<JoinNodeTransaction>
+  MaybeCreate(EditorBase& aEditorBase, nsINode& aLeftNode, nsINode& aRightNode);
 
   /**
    * CanDoIt() returns true if there are enough members and can join or