Moved JsonPrefStore to use SequencedWorkerPool

chrome/common/json_pref_store.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_COMMON_JSON_PREF_STORE_H_
 #define CHROME_COMMON_JSON_PREF_STORE_H_
 
 #include <set>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "chrome/common/important_file_writer.h"
 #include "chrome/common/persistent_pref_store.h"
 
 namespace base {
 class DictionaryValue;
-class MessageLoopProxy;
+class SequencedWorkerPool;
+class SequencedTaskRunner;
 class Value;
 }
 
 class FilePath;
 
 // A writable PrefStore implementation that is used for user preferences.
 class JsonPrefStore : public PersistentPrefStore,
                       public ImportantFileWriter::DataSerializer {
  public:
-  // |file_message_loop_proxy| is the MessageLoopProxy for a thread on which
-  // file I/O can be done.
-  JsonPrefStore(const FilePath& pref_filename,
-                base::MessageLoopProxy* file_message_loop_proxy);
+  // Returns instance of SequencedTaskRunner which guarantees that file
+  // operations on the same file will be executed in sequenced order.
+  static scoped_refptr<base::SequencedTaskRunner> GetTaskRunnerForFile(

[akalin, 2012/10/19 23:12:21]

as discussed, please make this return a raw pointer

[zel, 2012/10/21 20:03:19]

Done.

+      const FilePath& pref_filename,
+      base::SequencedWorkerPool* worker_pool);
+
+  // Creates an instance JsonPrefStore for a given |pref_filename| that will
+  // perform all file I/O operations on |sequenced_task_runner|.
+  // |sequenced_task_runner| must be a shutdown-blocking task runner, ideally
+  // created by GetTaskRunnerForFile() method above.
+  static JsonPrefStore* Create(
+      const FilePath& pref_filename,
+      base::SequencedTaskRunner* sequenced_task_runner);
 
   // PrefStore overrides:
   virtual ReadResult GetValue(const std::string& key,
                               const base::Value** result) const OVERRIDE;
   virtual void AddObserver(PrefStore::Observer* observer) OVERRIDE;
   virtual void RemoveObserver(PrefStore::Observer* observer) OVERRIDE;
   virtual size_t NumberOfObservers() const OVERRIDE;
   virtual bool IsInitializationComplete() const OVERRIDE;
 
   // PersistentPrefStore overrides:
@@ skipping 11 matching lines @@
   virtual void CommitPendingWrite() OVERRIDE;
   virtual void ReportValueChanged(const std::string& key) OVERRIDE;
 
   // This method is called after JSON file has been read. Method takes
   // ownership of the |value| pointer. Note, this method is used with
   // asynchronous file reading, so class exposes it only for the internal needs.
   // (read: do not call it manually).
   void OnFileRead(base::Value* value_owned, PrefReadError error, bool no_dir);
 
  private:
+  // |sequenced_task_runner| is a SequencedTaskRunner on which file I/O can

[akalin, 2012/10/19 23:12:21]

remove 'can'

[zel, 2012/10/21 20:03:19]

As I explained, that would be either cause a crash (confirmed in tests) or we
also need to change declaration of:

scoped_refptr<SequencedTaskRunner>
SequencedWorkerPool::GetSequencedTaskRunnerWithShutdownBehavior()

+  // will be run.
+  JsonPrefStore(const FilePath& pref_filename,
+                base::SequencedTaskRunner* sequenced_task_runner);
   virtual ~JsonPrefStore();
 
   // ImportantFileWriter::DataSerializer overrides:
   virtual bool SerializeData(std::string* output) OVERRIDE;
 
   FilePath path_;
-  scoped_refptr<base::MessageLoopProxy> file_message_loop_proxy_;
+  const scoped_refptr<base::SequencedTaskRunner> sequenced_task_runner_;
 
   scoped_ptr<base::DictionaryValue> prefs_;
 
   bool read_only_;
 
   // Helper for safely writing pref data.
   ImportantFileWriter writer_;
 
   ObserverList<PrefStore::Observer, true> observers_;
 
   scoped_ptr<ReadErrorDelegate> error_delegate_;
 
   bool initialized_;
   PrefReadError read_error_;
 
   std::set<std::string> keys_need_empty_value_;
 
   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 };
 
 #endif  // CHROME_COMMON_JSON_PREF_STORE_H_