WebUI Polymer2: Filter out material history item test

The test is failing (flaky?) on Mac 10.12.

Bug: 874976
Change-Id: I913c6d39d7650e8298cd83eb2236f0f0d027f5d1
Reviewed-on: https://chromium-review.googlesource.com/1178639
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583956}

chrome/test/data/webui/md_history/md_history_browsertest.js

@@ -82,12 +82,9 @@ MaterialHistoryItemTest.prototype = {
   ]),
 };
 
-// https://crbug.com/874976, fails on Mac.
-GEN('#if !defined(OS_MACOSX)');
 TEST_F('MaterialHistoryItemTest', 'All', function() {
   mocha.run();
 });
-GEN('#endif');
 
 function MaterialHistoryListTest() {}
 

testing/buildbot/filters/webui_polymer2_browser_tests.filter

@@ -40,6 +40,9 @@
 -PrintPreviewDestinationListTest.FireDestinationSelected
 -SettingsAdvancedPageBrowserTest.Load
 
+# Mac only failure. See crbug.com/874976
+-MaterialHistoryItemTest.All
+
 # Tests that fail only on official builds.
 -CrSettingsChromeCleanupPageTest.All
 -CrSettingsIncompatibleApplicationsPageTest.All