Extracted inner class doing process dispatch.

chrome/browser/web_resource/json_asynchronous_unpacker.h

+// Copyright (c) 2012 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_WEB_RESOURCE_JSON_ASYNCHRONOUS_UNPACKER_H_
+#define CHROME_BROWSER_WEB_RESOURCE_JSON_ASYNCHRONOUS_UNPACKER_H_
+
+#include <string>
+
+#include "base/values.h"
+
+// A delegate interface for users of JSONAsynchronousUnpacker.
+class JSONAsynchronousUnpackerDelegate {
+ public:
+  virtual ~JSONAsynchronousUnpackerDelegate() {}
+
+  // This will be called when the response is parsed properly. |parsed_json|
+  // contains the decoded information.
+  virtual void OnUnpackFinished(const DictionaryValue& parsed_json) = 0;
+
+  // This will be called if there is an error while parsing the data.
+  virtual void OnUnpackError(const std::string& error_message) = 0;
+};
+
+// This class coordinates a web resource unpack and parse task which is run
+// asynchronously.  Results are sent back to the delegate via one of its
+// OnUnpack<xxx> methods.
+class JSONAsynchronousUnpacker {
+ public:
+  // Creates a WebResourceServiceUnpacker appropriate for the platform. The
+  // delegate must be kept around until one of the delegate methods is called.
+  // In case the delegate is no longer valid, ClearDelegate() must be called.
+  static JSONAsynchronousUnpacker*
+      Create(JSONAsynchronousUnpackerDelegate* delegate);
+
+  virtual ~JSONAsynchronousUnpacker() {}
+
+  // Start the decoding. The concrete implementation should delete itself after
+  // calling the delegate method.
+  virtual void Start(const std::string& json_data) = 0;
+
+  // If the delegate is going away it needs to inform the unpacker about it.
+  void ClearDelegate() {
+    delegate_ = NULL;
+  };
+
+ protected:
+  explicit JSONAsynchronousUnpacker(JSONAsynchronousUnpackerDelegate* delegate)
+      : delegate_(delegate) {
+  }
+
+  JSONAsynchronousUnpackerDelegate* delegate_;
+};
+
+#endif  // CHROME_BROWSER_WEB_RESOURCE_JSON_ASYNCHRONOUS_UNPACKER_H_