Make it possible to build without enable_supervised_users.

chrome/browser/ui/webui/browsing_history_handler.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/browsing_history_handler.h"
 
 #include <stddef.h>
 
 #include <set>
 #include <utility>
@@ skipping 39 matching lines @@
 #include "chrome/browser/supervised_user/supervised_user_service_factory.h"
 #include "chrome/browser/supervised_user/supervised_user_url_filter.h"
 #endif
 
 #if defined(OS_ANDROID)
 #include "chrome/browser/android/preferences/preferences_launcher.h"
 #else
 #include "chrome/common/chrome_features.h"
 #endif
 
+class SupervisedUserService;
+
 using bookmarks::BookmarkModel;
 
 namespace {
 
 // Identifiers for the type of device from which a history entry originated.
 static const char kDeviceTypeLaptop[] = "laptop";
 static const char kDeviceTypePhone[] = "phone";
 static const char kDeviceTypeTablet[] = "tablet";
 
 // Returns a localized version of |visit_time| including a relative
@@ skipping 462 matching lines @@
   web_ui()->CallJavascriptFunctionUnsafe("historyDeleted");
 }
 
 void BrowsingHistoryHandler::HasOtherFormsOfBrowsingHistory(
     bool has_other_forms,
     bool has_synced_results) {
   web_ui()->CallJavascriptFunctionUnsafe("showNotification",
                                          base::Value(has_synced_results),
                                          base::Value(has_other_forms));
 }