[WebHID] Change some interfaces to dictionaries

This CL changes HIDCollectionInfo, HIDReportInfo, and HIDReportItem
interfaces to dictionaries for easier logging with JSON and to avoid
polluting the window web namespace.

Spec: WICG/webhid#22
Test: https://webhid-collections.glitch.me/

Change-Id: Ife8d089505312bba9f42e5d8fb1c466f44bd8e45
Bug: 890096

webhid/idlharness.https.window.js

@@ -14,9 +14,6 @@ idl_test(
       Navigator: ['navigator'],
       // TODO: HIDConnectionEvent
       // TODO: HIDInputReportEvent
-      // TODO: HIDReportItem
-      // TODO: HIDReportInfo
-      // TODO: HIDCollectionInfo
       // TODO: HIDDevice
     });
   }