MD History: Improve test helpers, update synced tabs tests to use them

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 147 matching lines @@
   source->AddResourcePath("list_container.html",
                           IDR_MD_HISTORY_LIST_CONTAINER_HTML);
   source->AddResourcePath("list_container.js",
                           IDR_MD_HISTORY_LIST_CONTAINER_JS);
   source->AddResourcePath("searched_label.html",
                           IDR_MD_HISTORY_SEARCHED_LABEL_HTML);
   source->AddResourcePath("searched_label.js",
                           IDR_MD_HISTORY_SEARCHED_LABEL_JS);
   source->AddResourcePath("shared_style.html",
                           IDR_MD_HISTORY_SHARED_STYLE_HTML);
+  source->AddResourcePath("shared_vars.html",
+                          IDR_MD_HISTORY_SHARED_VARS_HTML);
   source->AddResourcePath("side_bar.html", IDR_MD_HISTORY_SIDE_BAR_HTML);
   source->AddResourcePath("side_bar.js", IDR_MD_HISTORY_SIDE_BAR_JS);
   source->AddResourcePath("synced_device_card.html",
                           IDR_MD_HISTORY_SYNCED_DEVICE_CARD_HTML);
   source->AddResourcePath("synced_device_card.js",
                           IDR_MD_HISTORY_SYNCED_DEVICE_CARD_JS);
   source->AddResourcePath("synced_device_manager.html",
                           IDR_MD_HISTORY_SYNCED_DEVICE_MANAGER_HTML);
   source->AddResourcePath("synced_device_manager.js",
                           IDR_MD_HISTORY_SYNCED_DEVICE_MANAGER_JS);
@@ skipping 38 matching lines @@
   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);
 }