--- a/.eslintignore
+++ b/.eslintignore
@@ -107,17 +107,17 @@ devtools/client/webconsole/**
 !devtools/client/webconsole/jsterm.js
 !devtools/client/webconsole/console-commands.js
 devtools/client/webide/**
 devtools/server/**
 !devtools/server/actors/webbrowser.js
 !devtools/server/actors/styles.js
 devtools/shared/*.js
 !devtools/shared/css-lexer.js
-!devtools/shared/promise_defer.js
+!devtools/shared/defer.js
 !devtools/shared/task.js
 devtools/shared/*.jsm
 devtools/shared/apps/**
 devtools/shared/client/**
 devtools/shared/discovery/**
 devtools/shared/gcli/**
 !devtools/shared/gcli/templater.js
 devtools/shared/heapsnapshot/**

rename from devtools/shared/promise_defer.js
rename to devtools/shared/defer.js

--- a/devtools/shared/moz.build
+++ b/devtools/shared/moz.build
@@ -39,22 +39,22 @@ JAR_MANIFESTS += ['jar.mn']
 
 DevToolsModules(
     'async-storage.js',
     'async-utils.js',
     'builtin-modules.js',
     'content-observer.js',
     'css-lexer.js',
     'css-parsing-utils.js',
+    'defer.js',
     'deprecated-sync-thenables.js',
     'DevToolsUtils.js',
     'event-emitter.js',
     'event-parsers.js',
     'indentation.js',
     'Loader.jsm',
     'Parser.jsm',
     'path.js',
-    'promise_defer.js',
     'protocol.js',
     'system.js',
     'task.js',
     'ThreadSafeDevToolsUtils.js',
 )

rename from devtools/shared/tests/unit/test_promise_defer.js
rename to devtools/shared/tests/unit/test_defer.js
--- a/devtools/shared/tests/unit/test_promise_defer.js
+++ b/devtools/shared/tests/unit/test_defer.js
@@ -1,17 +1,17 @@
 /* -*- js-indent-level: 2; indent-tabs-mode: nil -*- */
 /* Any copyright is dedicated to the Public Domain.
    http://creativecommons.org/publicdomain/zero/1.0/ */
 
 "use strict";
 
 var Cu = Components.utils;
 var {require} = Cu.import("resource://devtools/shared/Loader.jsm", {});
-const defer = require("devtools/shared/promise_defer");
+const defer = require("devtools/shared/defer");
 
 function testResolve() {
   const deferred = defer();
   deferred.resolve("success");
   return deferred.promise;
 }
 
 function testReject() {

--- a/devtools/shared/tests/unit/xpcshell.ini
+++ b/devtools/shared/tests/unit/xpcshell.ini
@@ -21,10 +21,10 @@ support-files =
 [test_safeErrorString.js]
 [test_defineLazyPrototypeGetter.js]
 [test_async-utils.js]
 [test_console_filtering.js]
 [test_prettifyCSS.js]
 [test_require_lazy.js]
 [test_require.js]
 [test_stack.js]
-[test_promise_defer.js]
+[test_defer.js]
 [test_executeSoon.js]