Add return value and update docs. Fixes #1966.

src/standard/notify-path.html

@@ -65,13 +65,18 @@
 
     Polymer.Base._addFeature({
       /**
-        Notify that a path has changed. For example:
-
-            this.item.user.name = 'Bob';
-            this.notifyPath('item.user.name', this.item.user.name);
-
-        Returns true if notification actually took place, based on
-        a dirty check of whether the new value was already known
+       * Notify that a path has changed. For example:
+       *
+       *   this.item.user.name = 'Bob';
+       *   this.notifyPath('item.user.name', this.item.user.name);
+       *
+       * @param {string} path Path that should be notified.
+       * @param {*} value Value of the specified path.
+       * @param {boolean=} fromAbove When true, specifies that the change came
+       *   from above this element and thus upward notification is not
+       *   necessary.
+       * @return {boolean} Returns true if notification actually took place,
+       *   based on a dirty check of whether the new value was already known.
       */
       notifyPath: function(path, value, fromAbove) {
         var old = this._propertySetter(path, value);
@@ -92,6 +97,7 @@
             this._notifyPath(path, value);
           }
           // console.groupEnd((this.localName || this.dataHost.id + '-' + this.dataHost.dataHost.index) + '#' + (this.id || this.index) + ' ' + path, value);
+          return true;
         }
       },