Add placeholder to textarea as well as text

IPython/html/static/widgets/js/widget_string.js

@@ -71,6 +71,11 b' define(["widgets/js/widget"], function(WidgetManager){'
             this.update(); // Set defaults.
 
             this.model.on('msg:custom', $.proxy(this._handle_textarea_msg, this));
+            this.model.on('change:placeholder', function(model, value, options) {
+                this.update_placeholder(value);
+            }, this);
+
+            this.update_placeholder();
         },
 
         _handle_textarea_msg: function (content){
@@ -80,6 +85,13 b' define(["widgets/js/widget"], function(WidgetManager){'
             }
         },
 
+        update_placeholder: function(value) {
+            if (!value) {
+                value = this.model.get('placeholder');
+            }
+            this.$textbox.attr('placeholder', value);
+        },
+
         scroll_to_bottom: function (){
             // Scroll the text-area view to the bottom.
             this.$textbox.scrollTop(this.$textbox[0].scrollHeight);