Convert //ios from scoped_ptr to std::unique_ptr.

ios/web/public/web_thread.h

 // 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.
 
 #ifndef IOS_WEB_PUBLIC_WEB_THREAD_H_
 #define IOS_WEB_PUBLIC_WEB_THREAD_H_
 
 #include <string>
 
 #include "base/callback_forward.h"
@@ skipping 240 matching lines @@
   //           Foo, web::WebThread::DeleteOnIOThread> {
   //
   // ...
   //  private:
   //   friend struct web::WebThread::DeleteOnThread<web::WebThread::IO>;
   //   friend class base::DeleteHelper<Foo>;
   //
   //   ~Foo();
   //
   // Sample usage with scoped_ptr:
-  // scoped_ptr<Foo, web::WebThread::DeleteOnIOThread> ptr;
+  // std::unique_ptr<Foo, web::WebThread::DeleteOnIOThread> ptr;
   struct DeleteOnUIThread : public DeleteOnThread<UI> {};
   struct DeleteOnIOThread : public DeleteOnThread<IO> {};
   struct DeleteOnFileThread : public DeleteOnThread<FILE> {};
   struct DeleteOnDBThread : public DeleteOnThread<DB> {};
 
  private:
   friend class WebThreadImpl;
 
   WebThread() {}
   DISALLOW_COPY_AND_ASSIGN(WebThread);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_PUBLIC_WEB_THREAD_H_