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

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 cr.define('md_history.history_item_test', function() {
   function registerTests() {
     suite('history-item', function() {
       var element;
       var TEST_HISTORY_RESULTS;
       var SEARCH_HISTORY_RESULTS;
@@ skipping 58 matching lines @@
           // Checks that a new time gap separator has been inserted.
           assertTrue(items[2].hasTimeGap);
 
           element.removeDeletedHistory_([element.historyData_[3]]);
 
           // Checks time gap separator is removed.
           assertFalse(items[2].hasTimeGap);
         });
       });
 
+      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 = '';
       });
     });
   }
   return {
     registerTests: registerTests
   };
 });