MD History: Trim long item titles to reduce effect on performance

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

Index: chrome/test/data/webui/md_history/history_item_test.js
diff --git a/chrome/test/data/webui/md_history/history_item_test.js b/chrome/test/data/webui/md_history/history_item_test.js
index 77700e3cb3ca3809dded16d970ad1fa47a02b1df..9ab28b9d823af8bfa739b9f6f0c4f8a84b1c5e66 100644
--- a/chrome/test/data/webui/md_history/history_item_test.js
+++ b/chrome/test/data/webui/md_history/history_item_test.js
@@ -76,6 +76,16 @@ cr.define('md_history.history_item_test', function() {
         });
       });
 
+      test('long titles are trimmed', function() {
+        var item = document.createElement('history-item');
+        var longtitle = '0123456789'.repeat(100);
+        item.item =
+            createHistoryEntry('2016-06-30', 'http://example.com/' + longtitle);
+
+        var label = item.$$('history-searched-label');
+        assertEquals(TITLE_MAX_LENGTH, label.title.length);
+      });
+
       teardown(function() {
         element.historyData_ = [];
         element.searchedTerm = '';