Adds async interface method to PersistentPrefStore.

chrome/common/persistent_pref_store.h

 // Copyright (c) 2011 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_PERSISTENT_PREF_STORE_H_
 #define CHROME_COMMON_PERSISTENT_PREF_STORE_H_
 #pragma once
 
 #include <string>
 
@@ skipping 16 matching lines @@
     PREF_READ_ERROR_JSON_TYPE,
     PREF_READ_ERROR_ACCESS_DENIED,
     PREF_READ_ERROR_FILE_OTHER,
     PREF_READ_ERROR_FILE_LOCKED,
     PREF_READ_ERROR_NO_FILE,
     PREF_READ_ERROR_JSON_REPEAT,
     PREF_READ_ERROR_OTHER,
     PREF_READ_ERROR_FILE_NOT_SPECIFIED
   };
 
+  class ReadErrorDelegate {
+   public:
+    virtual ~ReadErrorDelegate() {}
+
+    virtual void OnError(PrefReadError error) = 0;
+  };
+
   // Equivalent to PrefStore::GetValue but returns a mutable value.
   virtual ReadResult GetMutableValue(const std::string& key,
                                      Value** result) = 0;
 
   // Triggers a value changed notification. This function needs to be called
   // if one retrieves a list or dictionary with GetMutableValue and change its
   // value. SetValue takes care of notifications itself. Note that
   // ReportValueChanged will trigger notifications even if nothing has changed.
   virtual void ReportValueChanged(const std::string& key) = 0;
 
   // Sets a |value| for |key| in the store. Assumes ownership of |value|, which
   // must be non-NULL.
   virtual void SetValue(const std::string& key, Value* value) = 0;
 
   // Same as SetValue, but doesn't generate notifications. This is used by
   // PrefService::GetMutableUserPref() in order to put empty entries
   // into the user pref store. Using SetValue is not an option since existing
   // tests rely on the number of notifications generated.
   virtual void SetValueSilently(const std::string& key, Value* value) = 0;
 
   // Removes the value for |key|.
   virtual void RemoveValue(const std::string& key) = 0;
 
   // Whether the store is in a pseudo-read-only mode where changes are not
   // actually persisted to disk.  This happens in some cases when there are
   // read errors during startup.
   virtual bool ReadOnly() const = 0;
 
-  // Reads the preferences from disk.
+  // Reads the preferences from disk. Notifies observers via
+  // "PrefStore::OnInitializationCompleted" when done.
   virtual PrefReadError ReadPrefs() = 0;
 
+  // Reads the preferences from disk asynchronously. Notifies observers via
+  // "PrefStore::OnInitializationCompleted" when done. Also it fires
+  // |error_delegate| if it is not NULL and reading error has occurred.
+  // Owns |error_delegate|.
+  virtual void ReadPrefsAsync(ReadErrorDelegate* error_delegate) = 0;
+
   // Writes the preferences to disk immediately.
   virtual bool WritePrefs() = 0;
 
   // Schedules an asynchronous write operation.
   virtual void ScheduleWritePrefs() = 0;
 
   // Lands any pending writes to disk.
   virtual void CommitPendingWrite() = 0;
 };
 
 #endif  // CHROME_COMMON_PERSISTENT_PREF_STORE_H_