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

chrome/browser/ui/webui/md_history_ui.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/ui/webui/md_history_ui.h"
 
 #include "base/command_line.h"
 #include "build/build_config.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/signin/signin_manager_factory.h"
@@ skipping 195 matching lines @@
 
 // static
 bool MdHistoryUI::IsEnabled(Profile* profile) {
   return base::FeatureList::IsEnabled(features::kMaterialDesignHistory) &&
          !base::CommandLine::ForCurrentProcess()->HasSwitch(
              switches::kHistoryEnableGroupByDomain) &&
          !profile->IsSupervised();
 }
 
 // static
-void MdHistoryUI::DisableForTesting() {
+void MdHistoryUI::SetEnabledForTesting(bool enabled) {
   std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
-  feature_list->InitializeFromCommandLine(
-      std::string(), features::kMaterialDesignHistory.name);
+
+  const std::string& name = features::kMaterialDesignHistory.name;
+  feature_list->InitializeFromCommandLine(enabled ? name : "",
+                                          enabled ? "" : name);
   base::FeatureList::ClearInstanceForTesting();
   base::FeatureList::SetInstance(std::move(feature_list));
 }
 
 // static
 base::RefCountedMemory* MdHistoryUI::GetFaviconResourceBytes(
     ui::ScaleFactor scale_factor) {
   return ResourceBundle::GetSharedInstance().LoadDataResourceBytesForScale(
       IDR_HISTORY_FAVICON, scale_factor);
 }