Media Galleries API Picasa: Make PicasaDataProvider handle async PMP and INI parsing robustly.

chrome/browser/media_galleries/fileapi/safe_picasa_album_table_reader.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 CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_PICASA_ALBUM_TABLE_READER_H_
 #define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_PICASA_ALBUM_TABLE_READER_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 13 matching lines @@
 
 namespace picasa {
 
 // SafePicasaAlbumTableReader parses the given Picasa PMP Album Table safely
 // via a utility process. The SafePicasaAlbumTableReader object is ref-counted
 // and kept alive after Start() is called until the ParserCallback is called.
 // The ParserCallback is guaranteed to be called eventually either when the
 // utility process replies or when it dies.
 class SafePicasaAlbumTableReader : public content::UtilityProcessHostClient {
  public:
-  typedef base::Callback<void(bool,
+  // PicasaDataProvider keeps a reference to the last-dispatched instance of
+  // this class so it can ignore callbacks from 'stale' instances. The callback
+  // also keeps a reference so it doesn't get destroyed prematurely.
+  typedef base::Callback<void(scoped_refptr<SafePicasaAlbumTableReader>,
+                              bool parse_success,
                               const std::vector<AlbumInfo>&,
-                              const std::vector<AlbumInfo>&)> ParserCallback;
+                              const std::vector<AlbumInfo>&)>
+      ParserCallback;
 
   SafePicasaAlbumTableReader(const AlbumTableFiles& album_table_files,
                              const ParserCallback& callback);
 
   void Start();
 
  private:
   enum ParserState {
     INITIAL_STATE,
     PINGED_UTILITY_PROCESS_STATE,
@@ skipping 35 matching lines @@
   // Verifies the messages from the utility process came at the right time.
   // Initialized on the Media Task Runner, but only accessed on the IO thread.
   ParserState parser_state_;
 
   DISALLOW_COPY_AND_ASSIGN(SafePicasaAlbumTableReader);
 };
 
 }  // namespace picasa
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_PICASA_ALBUM_TABLE_READER_H_