message: fix(upgrade): use quote to prevent ClossureCompiler obfuscating $event.
  This is critical for AngularJS to get the $event object in template.
diff: @@ -165,7 +165,7 @@ export class DowngradeComponentAdapter {
  next: assignExpr ?
  ((setter: any) => (v: any /** TODO #9100 */) => setter(this.scope, v))(setter) :
  ((getter: any) => (v: any /** TODO #9100 */) =>
  - getter(this.scope, {$event: v}))(getter)
  + getter(this.scope, {'$event': v}))(getter)
  });
  } else {
  throw new Error(
  