Fixme comment + whatsnew

docs/source/whatsnew/pr/deprecation-js-container.rst

@@ -0,0 +1,3 b''
+* calling `container.show()` on javascript display is deprecated and will
+  trigger errors on future IPython notebook versions. `container` now show
+  itself as soon as non-empty

IPython/html/static/notebook/js/outputarea.js

@@ -558,9 +558,11 b' var IPython = (function (IPython) {'
         var toinsert = this.create_output_subarea(md, "output_javascript", type);
         IPython.keyboard_manager.register_events(toinsert);
         element.append(toinsert);
+        // FIXME TODO : remove `container element for 3.0` 
         //backward compat, js should be eval'ed in a context where `container` is defined.
         var container = element;
         container.show = function(){console.log('Warning "container.show()" is deprecated.')};
+        // end backward compat
         try {
             eval(js);
         } catch(err) {