polymer-localstorage: add autoSaveDisabled to disable auto save

Author: frankiefu

polymer-localstorage/polymer-localstorage.html

@@ -63,6 +63,14 @@
        * @default false
        */
       useRaw: false,
+      /**
+       * If true, auto save is disabled.
+       *
+       * @attribute audoSaveDisabled
+       * @type boolean
+       * @default false
+       */
+      audoSaveDisabled: false,
       enteredDocument: function() {
         // wait for bindings are all setup
         this.async('load');