Also disable HistoryWebUITest.multipleSelect on Mac due to flakeness.

chrome/test/data/webui/history_browsertest.js

Index: chrome/test/data/webui/history_browsertest.js
diff --git a/chrome/test/data/webui/history_browsertest.js b/chrome/test/data/webui/history_browsertest.js
index 1a08f337c1692794827147d2d9c12b645e1154a8..5913041c001c628703c2e651733f7ed51ad6b65a 100644
--- a/chrome/test/data/webui/history_browsertest.js
+++ b/chrome/test/data/webui/history_browsertest.js
@@ -506,9 +506,9 @@ TEST_F('HistoryWebUITest', 'DISABLED_bulkDeletion', function() {
 
 /**
  * Test selecting multiple entries using shift click.
- * Disabled due to time out on win: crbug/375910
+ * Disabled due to time out on win and mac: crbug/375910
  */
-GEN('#if defined(OS_WIN)');
+GEN('#if defined(OS_WIN) || defined(OS_MACOSX)');
 GEN('#define MAYBE_multipleSelect DISABLED_multipleSelect');
 GEN('#else');
 GEN('#define MAYBE_multipleSelect multipleSelect');