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

chrome/browser/history/history_browsertest.cc

Index: chrome/browser/history/history_browsertest.cc
diff --git a/chrome/browser/history/history_browsertest.cc b/chrome/browser/history/history_browsertest.cc
index b74e36466b731f776b3c991a8d0a55009f38fc56..8a12511c449c2c7d3fd6683715314412e15c5383 100644
--- a/chrome/browser/history/history_browsertest.cc
+++ b/chrome/browser/history/history_browsertest.cc
@@ -296,7 +296,7 @@ IN_PROC_BROWSER_TEST_F(HistoryBrowserTest,
 IN_PROC_BROWSER_TEST_F(HistoryBrowserTest, MAYBE_HistorySearchXSS) {
   // TODO(tsergeant): Enable this test on MD History once it is possible to pass
   // in a query via URL (crbug.com/619799).
-  MdHistoryUI::DisableForTesting();
+  MdHistoryUI::SetEnabledForTesting(false);
 
   GURL url(std::string(chrome::kChromeUIHistoryURL) +
       "#q=%3Cimg%20src%3Dx%3Ax%20onerror%3D%22document.title%3D'XSS'%22%3E");