[WebUI] Make HistoryListFocusTest.All works better with actual setTimeout 0

This is a follow-up fix for
https://chromium-review.googlesource.com/c/chromium/src/+/2600274/3/chrome/test/data/webui/test_util.js#135

- Reverted change to chrome/test/data/webui/test_util.js
- Make history_list_focus_test.js work better with actual setTimeout 0

Bug: 402694
Change-Id: I564a7d45678505ef7fe2af3820f7bfeb1101c256
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2600327Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: John Lee <johntlee@chromium.org>
Commit-Queue: Wanming Lin <wanming.lin@intel.com>
Cr-Commit-Position: refs/heads/master@{#840934}

chrome/test/data/webui/history/history_list_focus_test.js

@@ -146,6 +146,7 @@ suite('<history-list>', function() {
     assertEquals(4, element.historyData_.length);
     assertEquals(4, items.length);
     items[3].$['menu-button'].click();
+    await flushTasks();
     element.$$('#menuRemoveButton').click();
     assertNotEquals(items[2].$['menu-button'], element.lastFocused_);
     await testService.whenCalled('removeVisits');

chrome/test/data/webui/test_util.js

@@ -132,7 +132,7 @@ cr.define('test_util', function() {
     // Promises have microtask timing, so we use setTimeout to explicitly force
     // a new task.
     return new Promise(function(resolve, reject) {
-      window.setTimeout(resolve, 1);
+      window.setTimeout(resolve, 0);
     });
   }