fix dom-repeat sort on item update

Fixes Polymer#3626 by triggering a render when a single item changes in a
sorted/filtered dom-repeat.

src/lib/template/dom-repeat.html

@@ -369,11 +369,31 @@
       } else { // items.*
         // slice off 'items.' ('items.'.length == 6)
         var subpath = change.path.slice(6);
+        this._checkItemChanges(subpath);
         this._forwardItemPath(subpath, change.value);
         this._checkObservedPaths(subpath);
       }
     },
 
+    _checkItemChanges: function(path) {
+        var paths = path.split('.');
+        if (paths[0] === 'length') {
+            return;
+        }
+        if(this._sortFn || this._filterFn) {
+            // if an entire item has changed
+            if(paths.length === 1 && paths[0].indexOf('#') === 0) {
+                this._needFullRefresh = true;
+                if (this.delay) {
+                    this.debounce('render', this._render, this.delay);
+                } else {
+                    this._debounceTemplate(this._render);
+                }
+                return;
+            }
+        }
+    },
+
     _checkObservedPaths: function(path) {
       if (this._observePaths) {
         path = path.substring(path.indexOf('.') + 1);