Language settings: Wait 100ms to close language action menu on checkbox change

chrome/test/data/webui/settings/languages_page_browsertest.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** @fileoverview Suite of tests for settings-languages-page. */
 
 /** @const {string} Path to root from chrome/test/data/webui/settings/. */
 var ROOT_PATH = '../../../../../';
 
 // Polymer BrowserTest fixture.
@@ skipping 217 matching lines @@
         assertEquals(1, separator.offsetHeight);
 
         // Disable Translate. On platforms that can't change the UI language,
         // this hides all the checkboxes, so the separator isn't needed.
         // Chrome OS and Windows still show a checkbox and thus the separator.
         languageHelper.setPrefValue('translate.enabled', false);
         assertEquals(
             cr.isChromeOS || cr.isWindows ? 1 : 0, separator.offsetHeight);
       });
 
+      test('toggle translate', function(done) {
+        // Enable Translate so the menu always shows the Translate checkbox.
+        languageHelper.setPrefValue('translate.enabled', true);
+        languagesPage.set('languages.translateTarget', 'foo');
+        languagesPage.set('languages.enabled.1.supportsTranslate', true);
+
+        var languageOptionsDropdownTrigger =
+            languagesCollapse.querySelectorAll('paper-icon-button')[1];
+        assertTrue(!!languageOptionsDropdownTrigger);
+        MockInteractions.tap(languageOptionsDropdownTrigger);
+        assertTrue(actionMenu.open);
+
+        // Toggle the translate option.
+        var translateOption = actionMenu.querySelector('#offerTranslations');
+        assertTrue(!!translateOption);
+        assertFalse(translateOption.disabled);
+        MockInteractions.tap(translateOption);
+
+        // Menu should stay open briefly.
+        assertTrue(actionMenu.open);
+        // Guaranteed to run later than the menu close delay.

[dschuyler, 2017/01/14 01:15:36]

Could you point me to docs or something so I can understand why this would be
true? i.e. I would not intuitively expect that

setTimeout(..., 8);
and
setTimeout(..., 9);

will necessarily execute that that exact order. I would think that if they get
delayed they may pile up. iiuc, the guarantee is that they will not execute
sooner than the timeout, but may execute at some arbitrary time after the
timeout.

BTW, even if this didn't normally guarantee the order, I guess I only really
need to know that the order will guaranteed for chromium unit test (which may
help make the explanation easier). 

This seems to reinforce this (unless I'm misunderstanding these docs):
"There are a number of reasons why a timeout may take longer to fire than
anticipated." From
https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/se...

[michaelpg, 2017/01/14 04:39:13]

Totally right that the actual timeout is not guaranteed. But the callbacks are
well-ordered according to the spec, and the order is what matters. For these two
statements:

1. setTimeout(fn1, n1)
2. setTimeout(fn2, n2)

if n1 <= n2, fn1 runs before fn2. Thus kMenuCloseDelay + 1 ensures the menu
close callback has been called first.

Source:
https://html.spec.whatwg.org/multipage/webappapis.html#timer-initialisation-s...

The task (function) is not queued until after this step:

"Wait until any invocations of this algorithm that had the same method context
[window], that started before this one, and whose timeout is equal to or less
than this one's, have completed."

The task must be queued on the same task queue as other tasks from the "timer
task source", and tasks on a queue are executed in queue order.

[dschuyler, 2017/01/17 19:30:06]

Thanks! I really appreciate the detail provided.

+        setTimeout(function() {
+          assertFalse(actionMenu.open);
+          done();
+        }, settings.kMenuCloseDelay + 1);
+      });
+
       test('remove language', function() {
         var numEnabled = languagesPage.languages.enabled.length;
 
         // Enabled a language which we can then disable.
         var newLanguage = getAvailableLanguage();
         languageHelper.enableLanguage(newLanguage.code);
 
         // Wait for the language to be enabled.
         return whenNumEnabledLanguagesBecomes(numEnabled + 1).then(function() {
           // Populate the dom-repeat.
@@ skipping 73 matching lines @@
         assertTrue(!!languagesPage.$$('settings-edit-dictionary-page'));
       }
     });
   }.bind(this));
 
   // TODO(michaelpg): Test more aspects of the languages UI.
 
   // Run all registered tests.
   mocha.run();
 });