Revert of Move JoinString to the base namespace

ash/system/user/user_card_view.cc

 // Copyright 2014 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 "ash/system/user/user_card_view.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "ash/session/session_state_delegate.h"
@@ skipping 337 matching lines @@
   }
 }
 
 UserCardView::~UserCardView() {}
 
 void UserCardView::GetAccessibleState(ui::AXViewState* state) {
   state->role = ui::AX_ROLE_STATIC_TEXT;
   std::vector<base::string16> labels;
   for (int i = 0; i < child_count(); ++i)
     GetAccessibleLabelFromDescendantViews(child_at(i), labels);
-  state->name = base::JoinString(labels, base::ASCIIToUTF16(" "));
+  state->name = JoinString(labels, base::ASCIIToUTF16(" "));
 }
 
 void UserCardView::AddPublicModeUserContent(int max_width) {
   views::View* icon = CreateIcon(user::LOGGED_IN_PUBLIC, 0);
   AddChildView(icon);
   int details_max_width = max_width - icon->GetPreferredSize().width() -
                           kTrayPopupPaddingBetweenItems;
   AddChildView(new PublicAccountUserDetails(details_max_width));
 }
 
@@ skipping 96 matching lines @@
     content::BrowserContext* context =
         delegate->GetBrowserContextByIndex(multiprofile_index);
     icon->SetImage(delegate->GetUserInfo(context)->GetImage(),
                    gfx::Size(kTrayAvatarSize, kTrayAvatarSize));
   }
   return icon;
 }
 
 }  // namespace tray
 }  // namespace ash