Bug 1594786 - Make test.withHandlingUserInput to be only supported in automation. r=mixedpuppy,robwu

Make test.withHandingUserInput more restrictive than the rest of the test namespace
(which is also going to be available if an XPCSHELL_TEST_PROFILE_DIR environment var
is defined).

Differential Revision: https://phabricator.services.mozilla.com/D54498

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

toolkit/components/extensions/child/ext-test.js

@@ -123,6 +123,15 @@ this.test = class extends ExtensionAPI {
     return {
       test: {
         withHandlingUserInput(callback) {
+          // TODO(Bug 1598804): remove this once we don't expose anymore the
+          // entire test API namespace based on an environment variable.
+          if (!Cu.isInAutomation) {
+            // This dangerous method should only be available if the
+            // automation pref is set, which is the case in browser tests.
+            throw new ExtensionUtils.ExtensionError(
+              "withHandlingUserInput can only be called in automation"
+            );
+          }
           ExtensionCommon.withHandlingUserInput(
             context.contentWindow,
             callback