Disable MaterialHistoryItemTest.All on Mac

TBR=wjmaclean@chromium.org
NOTRY=true

Bug: 874976
Change-Id: I85a635544c5305bce8bb80ca3b2fedc50fd5a4fd
Reviewed-on: https://chromium-review.googlesource.com/1178310Reviewed-by: Xida Chen <xidachen@chromium.org>
Commit-Queue: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583730}

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

@@ -82,7 +82,14 @@ MaterialHistoryItemTest.prototype = {
   ]),
 };
 
-TEST_F('MaterialHistoryItemTest', 'All', function() {
+// https://crbug.com/874976, fails on Mac.
+GEN('#if defined(OS_MACOSX)');
+GEN('#define MAYBE_All DISABLED_All');
+GEN('#else');
+GEN('#define MAYBE_All All');
+GEN('#endif');
+
+TEST_F('MaterialHistoryItemTest', 'MAYBE_All', function() {
   mocha.run();
 });