Chrome Cleaner UI: Use BrowserThread's DeleteOnIOThread for ChromePromptImpl

chrome/browser/safe_browsing/chrome_cleaner/srt_chrome_prompt_impl.h

 // Copyright 2017 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 CHROME_BROWSER_SAFE_BROWSING_CHROME_CLEANER_SRT_CHROME_PROMPT_IMPL_H_
 #define CHROME_BROWSER_SAFE_BROWSING_CHROME_CLEANER_SRT_CHROME_PROMPT_IMPL_H_
 
 #include <memory>
 #include <set>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "components/chrome_cleaner/public/interfaces/chrome_prompt.mojom.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace safe_browsing {
 
-// Implementation of the ChromePrompt Mojo interface.
+// Implementation of the ChromePrompt Mojo interface. Must be constructed and
+// destructed on the IO thread.
 class ChromePromptImpl : public chrome_cleaner::mojom::ChromePrompt {
  public:
   using OnPromptUser = base::OnceCallback<void(
       std::unique_ptr<std::set<base::FilePath>>,
       chrome_cleaner::mojom::ChromePrompt::PromptUserCallback)>;
 
   ChromePromptImpl(chrome_cleaner::mojom::ChromePromptRequest request,
                    base::Closure on_connection_closed,
                    OnPromptUser on_prompt_user);
   ~ChromePromptImpl() override;
 
   void PromptUser(
       std::vector<chrome_cleaner::mojom::UwSPtr> removable_uws_found,
       chrome_cleaner::mojom::ElevationStatus elevation_status,
       chrome_cleaner::mojom::ChromePrompt::PromptUserCallback callback)
       override;
 
  private:
   mojo::Binding<chrome_cleaner::mojom::ChromePrompt> binding_;
   OnPromptUser on_prompt_user_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromePromptImpl);
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_CHROME_CLEANER_SRT_CHROME_PROMPT_IMPL_H_