[Bluetooth] Added role attribute to bluetooth_device_list_item.

Bug: 1007361
Change-Id: Ie4a54f11775559638e28b56dd251eb1dd1558848
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1879868Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: James Vecore <vecore@google.com>
Cr-Commit-Position: refs/heads/master@{#710080}

chrome/browser/resources/settings/bluetooth_page/bluetooth_device_list_item.js

@@ -32,6 +32,8 @@ Polymer({
     },
   },
 
+  hostAttributes: {role: 'button'},
+
   /**
    * @param {!Event} event
    * @private