reset cached scroll values when resizing

this is needed since scrollTop of scrollbar element can be reset to 0
when ace is moved in the document.

lib/ace/virtual_renderer.js

@@ -375,6 +375,9 @@ var VirtualRenderer = function(container, theme) {
 
         if (this.resizing)
             this.resizing = 0;
+        // reset cached values on scrollbars, needs to be removed when switching to non-native scrollbars
+        // see https://github.com/ajaxorg/ace/issues/2195
+        this.scrollBarV.scrollLeft = this.scrollBarV.scrollTop = null;
     };
     
     this.$updateCachedSize = function(force, gutterWidth, width, height) {