Make TabRestoreService::Entry noncopyable and fix up surrounding code.

components/sessions/content/content_platform_specific_tab_data.h

 // Copyright 2015 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 COMPONENTS_SESSIONS_CONTENT_CONTENT_PLATFORM_SPECIFIC_TAB_DATA_H_
 #define COMPONENTS_SESSIONS_CONTENT_CONTENT_PLATFORM_SPECIFIC_TAB_DATA_H_
 
 #include "base/memory/ref_counted.h"
 #include "components/sessions/core/live_tab.h"
 #include "components/sessions/core/sessions_export.h"
 #include "content/public/browser/session_storage_namespace.h"
 
 namespace content {
 class WebContents;
 }
 
 namespace sessions {
 
 // A //content-specific subclass of PlatformSpecificTabData that is used to
 // associate TabRestoreService::Tab instances with the
 // content::SessionStorageNamespace of the WebContents from which they were
 // created.
 class SESSIONS_EXPORT ContentPlatformSpecificTabData
     : public PlatformSpecificTabData {
+  scoped_refptr<content::SessionStorageNamespace> session_storage_namespace_;
+
  public:
   explicit ContentPlatformSpecificTabData(content::WebContents* web_contents);
   ContentPlatformSpecificTabData();
   ~ContentPlatformSpecificTabData() override;
 
   content::SessionStorageNamespace* session_storage_namespace() const {
     return session_storage_namespace_.get();
   }
-
- private:
-  // PlatformSpecificTabData:
-  std::unique_ptr<PlatformSpecificTabData> Clone() override;
-
-  scoped_refptr<content::SessionStorageNamespace> session_storage_namespace_;
 };
 
 }  // namespace sessions
 
 #endif  // COMPONENTS_SESSIONS_CONTENT_CONTENT_PLATFORM_SPECIFIC_TAB_DATA_H_