MD History: truncate title to 300 chars in C++ instead of JS

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 fd824d0fa192782229c719b6f0fea972151f3d2e..17f1425b6a77c790d33ea1939f5513c4d76ae086 100644
--- a/chrome/test/data/webui/md_history/history_item_test.js
+++ b/chrome/test/data/webui/md_history/history_item_test.js
@@ -97,16 +97,6 @@ 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 = '';