Make JSONParser a pure interface.

components/safe_json/safe_json_parser_impl.h

 // 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.
 
 #ifndef COMPONENTS_SAFE_JSON_SAFE_JSON_PARSER_H_
 #define COMPONENTS_SAFE_JSON_SAFE_JSON_PARSER_H_
 
 #include <string>
 
-#include "base/basictypes.h"
-#include "base/callback.h"
+#include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
+#include "components/safe_json/safe_json_parser.h"
 #include "content/public/browser/utility_process_host_client.h"
 
 namespace base {
 class ListValue;
-class SingleThreadTaskRunner;
+class SequencedTaskRunner;
 class Value;
 }
 
 namespace IPC {
 class Message;
 }
 
 namespace safe_json {
 
-// SafeJsonParser parses a given JSON safely via a utility process. The object
-// is ref-counted and kept alive after Start() is called until one of the two
-// callbacks is called.
-class SafeJsonParser : public content::UtilityProcessHostClient {
+class SafeJsonParserImpl : public content::UtilityProcessHostClient,
+                           public SafeJsonParser {
  public:
-  typedef base::Callback<void(scoped_ptr<base::Value>)> SuccessCallback;
-  typedef base::Callback<void(const std::string&)> ErrorCallback;
-
-  SafeJsonParser(const std::string& unsafe_json,
-                 const SuccessCallback& success_callback,
-                 const ErrorCallback& error_callback);
-
-  void Start();
+  SafeJsonParserImpl(const std::string& unsafe_json,
+                     const SuccessCallback& success_callback,
+                     const ErrorCallback& error_callback);
 
  private:
-  ~SafeJsonParser() override;
+  ~SafeJsonParserImpl() override;
 
   void StartWorkOnIOThread();
 
   void OnJSONParseSucceeded(const base::ListValue& wrapper);
   void OnJSONParseFailed(const std::string& error_message);
 
   void ReportResults();
   void ReportResultsOnOriginThread();
 
   // Implementing pieces of the UtilityProcessHostClient interface.
   bool OnMessageReceived(const IPC::Message& message) override;
 
+  // SafeJsonParser implementation.
+  void Start() override;
+
   const std::string unsafe_json_;
   SuccessCallback success_callback_;
   ErrorCallback error_callback_;
-  scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner_;
+  scoped_refptr<base::SequencedTaskRunner> caller_task_runner_;
 
   scoped_ptr<base::Value> parsed_json_;
   std::string error_;
 
-  DISALLOW_COPY_AND_ASSIGN(SafeJsonParser);
+  DISALLOW_COPY_AND_ASSIGN(SafeJsonParserImpl);
 };
 
 }  // namespace safe_json
 
 #endif  // COMPONENTS_SAFE_JSON_SAFE_JSON_PARSER_H_