Convert string16 to base::string16 in content.

content/shell/browser/shell_login_dialog_mac.mm

 // Copyright 2013 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 "content/shell/browser/shell_login_dialog.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
 #include "base/mac/bundle_locations.h"
@@ skipping 69 matching lines @@
 
 - (void)cancel {
   [NSApp endSheet:[alert_ window]];
   alert_.reset();
 }
 
 @end
 
 namespace content {
 
-void ShellLoginDialog::PlatformCreateDialog(const string16& message) {
+void ShellLoginDialog::PlatformCreateDialog(const base::string16& message) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   helper_ = [[ShellLoginDialogHelper alloc] init];
 
   // Show the modal dialog.
   NSAlert* alert = [helper_ alert];
   [alert setDelegate:helper_];
   [alert setInformativeText:base::SysUTF16ToNSString(message)];
   [alert setMessageText:@"Please log in."];
   [alert addButtonWithTitle:@"OK"];
   NSButton* other = [alert addButtonWithTitle:@"Cancel"];
@@ skipping 12 matching lines @@
   [helper_ release];
   helper_ = nil;
 }
 
 void ShellLoginDialog::PlatformRequestCancelled() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   [helper_ cancel];
 }
 
 }  // namespace content