Disable MaterialHistoryItemTest.All on Mac

TBR=wjmaclean@chromium.org

Bug: 874976
Change-Id: I6973e2de0fb52dbfe5cec8319a02507736603243
Reviewed-on: https://chromium-review.googlesource.com/1178476Reviewed-by: Xida Chen <xidachen@chromium.org>
Reviewed-by: James MacLean <wjmaclean@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583825}

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

@@ -82,9 +82,12 @@ 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() {}