Bug 923719: Uplift Addon SDK to Firefox. r=me

bece20a...24471bc

addon-sdk/source/lib/sdk/test/utils.js

@@ -8,6 +8,9 @@ module.metadata = {
   'stability': 'unstable'
 };
 
+const { defer } = require('../core/promise');
+const { setInterval, clearInterval } = require('../timers');
+
 function getTestNames (exports)
   Object.keys(exports).filter(name => /^test/.test(name))
 
@@ -93,3 +96,14 @@ function after (exports, afterFn) {
   });
 }
 exports.after = after;
+
+function waitUntil (predicate, delay) {
+  let { promise, resolve } = defer();
+  let interval = setInterval(() => {
+    if (!predicate()) return;
+    clearInterval(interval);
+    resolve();
+  }, delay || 10);
+  return promise;
+}
+exports.waitUntil = waitUntil;