Use offset param instead of direction

notebook/static/notebook/js/actions.js

@@ -177,14 +177,14 @@ define(function(require){
             help: 'extend marked above',
             help_index : 'dc',
             handler : function (env) {
-                env.notebook.extend_marked('up');
+                env.notebook.extend_marked(1);
             }
         },
         'extend-marked-next' : {
             help: 'extend marked below',
             help_index : 'dd',
             handler : function (env) {
-                env.notebook.extend_marked('down');
+                env.notebook.extend_marked(-1);
             }
         },
         'cut-selected-cell' : {

notebook/static/notebook/js/notebook.js

@@ -716,13 +716,10 @@ define(function (require) {
     /**
      * Extend the selected range
      *
-     * @param {string} [direction='down'] - 'up' or 'down
+     * @param {number} offset
      */
-    Notebook.prototype.extend_marked = function(direction) {
-        
-        // Convert the direction to an index offset
-        var offset = direction === 'up' ? -1 : 1;
-        
+    Notebook.prototype.extend_marked = function(offset) {
+                
         // Mark currently selected cell
         this.get_selected_cell().marked = true;
         

notebook/tests/notebook/dualmode_merge.js

@@ -41,7 +41,7 @@ casper.notebook_test(function () {
         this.test.assertEquals(this.get_cell_text(1), 'cd', 'split; Verify that cell 1 has the second half.');
         this.validate_notebook_state('split', 'edit', 1);
         this.select_cell(0); // Move up to cell 0
-        this.evaluate(function() { IPython.notebook.extend_marked('down');});
+        this.evaluate(function() { IPython.notebook.extend_marked(1);});
         this.trigger_keydown('shift-m'); // Merge
         this.validate_notebook_state('merge', 'command', 0);
         this.test.assertEquals(this.get_cell_text(0), a, 'merge; Verify that cell 0 has the merged contents.');