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

components/sessions/content/content_platform_specific_tab_data.h

Index: components/sessions/content/content_platform_specific_tab_data.h
diff --git a/components/sessions/content/content_platform_specific_tab_data.h b/components/sessions/content/content_platform_specific_tab_data.h
index 1ccc6dd7c64448a5293bf466763f38a0cf73ecb7..fec5be5a1ec6ae2cfb5081252fce4935c93f55de 100644
--- a/components/sessions/content/content_platform_specific_tab_data.h
+++ b/components/sessions/content/content_platform_specific_tab_data.h
@@ -22,6 +22,8 @@ namespace sessions {
 // created.
 class SESSIONS_EXPORT ContentPlatformSpecificTabData
     : public PlatformSpecificTabData {
+  scoped_refptr<content::SessionStorageNamespace> session_storage_namespace_;
+
  public:
   explicit ContentPlatformSpecificTabData(content::WebContents* web_contents);
   ContentPlatformSpecificTabData();
@@ -30,12 +32,6 @@ class SESSIONS_EXPORT ContentPlatformSpecificTabData
   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