Bug 1566367 - [0.0] Fix javadoc in WebExtensionController. r=snorp

Differential Revision: https://phabricator.services.mozilla.com/D40773

--HG--
extra : moz-landing-system : lando

mobile/android/geckoview/src/main/java/org/mozilla/geckoview/WebExtensionController.java

@@ -36,6 +36,7 @@ public class WebExtensionController {
          * @param source An instance of {@link WebExtension} or null if extension was not registered
          *               with GeckoRuntime.registerWebextension
          * @param session An instance of {@link GeckoSession} to be closed.
+         * @return GeckoResult.ALLOW if the tab will be closed, GeckoResult.DENY otherwise
          */
         @UiThread
         @NonNull