[MD History] Disable Clear Browsing Data button for supervised users.

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

Index: chrome/test/data/webui/md_history/history_supervised_user_test.js
diff --git a/chrome/test/data/webui/md_history/history_supervised_user_test.js b/chrome/test/data/webui/md_history/history_supervised_user_test.js
index 4ac385a0429859b0d0b16e2f52866104a8f0f94a..a49d02306369fa8544aefbb506afd6fea0ceee48 100644
--- a/chrome/test/data/webui/md_history/history_supervised_user_test.js
+++ b/chrome/test/data/webui/md_history/history_supervised_user_test.js
@@ -44,6 +44,6 @@ suite('history-list supervised-user', function() {
   test('remove history menu button disabled', function() {
     var listContainer = app.$['history'];
     listContainer.$.sharedMenu.get();
-    assertTrue(listContainer.$$('#menuRemoveButton').disabled);
+    assertTrue(listContainer.$$('#menuRemoveButton').hidden);
   });
 });