Update Polymer from 1.2.1 -> 1.2.3

third_party/polymer/v1_0/components-chromium/iron-overlay-behavior/iron-overlay-behavior-extracted.js

 /**
 Use `Polymer.IronOverlayBehavior` to implement an element that can be hidden or shown, and displays
 on top of other content. It includes an optional backdrop, and can be used to implement a variety
 of UI controls including dialogs and drop downs. Multiple overlays may be displayed at once.
 
 ### Closing and canceling
 
 A dialog may be hidden by closing or canceling. The difference between close and cancel is user
 intent. Closing generally implies that the user acknowledged the content on the overlay. By default,
 it will cancel whenever the user taps outside it or presses the escape key. This behavior is
@@ skipping 398 matching lines @@
         this.refit();
       }
     }
 
 /**
  * Fired after the `iron-overlay` opens.
  * @event iron-overlay-opened
  */
 
 /**
+ * Fired when the `iron-overlay` is canceled, but before it is closed.
+ * Cancel the event to prevent the `iron-overlay` from closing.
+ * @event iron-overlay-canceled
+ */
+
+/**
  * Fired after the `iron-overlay` closes.
  * @event iron-overlay-closed
  * @param {{canceled: (boolean|undefined)}} set to the `closingReason` attribute
  */
   };
 
   /** @polymerBehavior */
   Polymer.IronOverlayBehavior = [Polymer.IronFitBehavior, Polymer.IronResizableBehavior, Polymer.IronOverlayBehaviorImpl];