Add base:: namespace to straggling string16s left in chrome/browser/ui.

chrome/browser/ui/cocoa/one_click_signin_bubble_controller.mm

 // Copyright (c) 2012 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.
 
 #import "chrome/browser/ui/cocoa/one_click_signin_bubble_controller.h"
 
 #include "base/strings/sys_string_conversions.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #import "chrome/browser/ui/cocoa/info_bubble_window.h"
 #import "chrome/browser/ui/cocoa/one_click_signin_view_controller.h"
@@ skipping 13 matching lines @@
                           webContents:(content::WebContents*)webContents
                          errorMessage:(NSString*)errorMessage
                              callback:(const BrowserWindow::StartSyncCallback&)
                                                                   syncCallback{
   viewController_.reset([[OneClickSigninViewController alloc]
       initWithNibName:@"OneClickSigninBubble"
           webContents:webContents
          syncCallback:syncCallback
         closeCallback:base::Bind(PerformClose, self)
          isSyncDialog:NO
-                email:string16()
+                email:base::string16()
          errorMessage:errorMessage]);
 
   NSWindow* parentWindow = [controller window];
 
   // Set the anchor point to right below the wrench menu.
   NSView* wrenchButton = [[controller toolbarController] wrenchButton];
   const NSRect bounds = [wrenchButton bounds];
   NSPoint anchorPoint = NSMakePoint(NSMidX(bounds), NSMaxY(bounds));
   anchorPoint = [wrenchButton convertPoint:anchorPoint toView:nil];
   anchorPoint = [parentWindow convertBaseToScreen:anchorPoint];
@@ skipping 20 matching lines @@
 - (OneClickSigninViewController*)viewController {
   return viewController_;
 }
 
 - (void)windowWillClose:(NSNotification*)notification {
   [viewController_ viewWillClose];
   [super windowWillClose:notification];
 }
 
 @end  // OneClickSigninBubbleController