Fix closure compile after Polymer update

third_party/polymer/v1_0/components-chromium/paper-behaviors/paper-ripple-behavior-extracted.js

 /** 
    * `Polymer.PaperRippleBehavior` dynamically implements a ripple 
    * when the element has focus via pointer or keyboard.
    *
    * NOTE: This behavior is intended to be used in conjunction with and after
    * `Polymer.IronButtonState` and `Polymer.IronControlState`.
    *
    * @polymerBehavior Polymer.PaperRippleBehavior 
    */
   Polymer.PaperRippleBehavior = {
@@ skipping 26 matching lines @@
     _downHandler: function(event) {
       Polymer.IronButtonStateImpl._downHandler.call(this, event);
       if (this.pressed) {
         this.ensureRipple(event);
       }
     },
 
     /**
      * Ensures this element contains a ripple effect. For startup efficiency 
      * the ripple effect is dynamically on demand when needed.
-     * @param {event} triggeringEvent (optional) event that triggered the 
+     * @param {!Event=} opt_triggeringEvent (optional) event that triggered the
      * ripple.
      */
-    ensureRipple: function(triggeringEvent) {
+    ensureRipple: function(opt_triggeringEvent) {
       if (!this.hasRipple()) {
         this._ripple = this._createRipple();
         this._ripple.noink = this.noink;
         var rippleContainer = this._rippleContainer || this.root;
         if (rippleContainer) {
           Polymer.dom(rippleContainer).appendChild(this._ripple);
         }
         var domContainer = rippleContainer === this.shadyRoot ? this : 
           rippleContainer;
-        if (triggeringEvent && domContainer.contains(triggeringEvent.target)) {
-          this._ripple.uiDownAction(triggeringEvent);
+        if (opt_triggeringEvent &&
+            domContainer.contains(opt_triggeringEvent.target)) {
+          this._ripple.uiDownAction(opt_triggeringEvent);
         }
       }
     },
 
     /**
      * Returns the `<paper-ripple>` element used by this element to create
      * ripple effects. The element's ripple is created on demand, when
      * necessary, and calling this method will force the 
      * ripple to be created.
      */
@@ skipping 18 matching lines @@
     _createRipple: function() {
       return document.createElement('paper-ripple');
     },
 
     _noinkChanged: function(noink) {
       if (this.hasRipple()) {
         this._ripple.noink = noink;
       }
     }
 
-  };
+  };