detect preferences errors

base/values.h

 // Copyright (c) 2009 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.
 
 // This file specifies a recursive data storage class called Value
 // intended for storing setting and other persistable data.
 // It includes the ability to specify (recursive) lists and dictionaries, so
 // it's fairly expressive.  However, the API is optimized for the common case,
 // namely storing a hierarchical tree of simple values.  Given a
 // DictionaryValue root, you can easily do things like:
@@ skipping 413 matching lines @@
 // This interface is implemented by classes that know how to serialize and
 // deserialize Value objects.
 class ValueSerializer {
  public:
   virtual ~ValueSerializer() {}
 
   virtual bool Serialize(const Value& root) = 0;
 
   // This method deserializes the subclass-specific format into a Value object.
   // If the return value is non-NULL, the caller takes ownership of returned
-  // Value. If the return value is NULL, and if error_message is non-NULL,
-  // error_message should be filled with a message describing the error.
-  virtual Value* Deserialize(std::string* error_message) = 0;
+  // Value. If the return value is NULL, and if error_code is non-NULL,
+  // error_code will be set with the underlying error.
+  // If |error_message| is non-null, it will be filled in with a formatted
+  // error message including the location of the error if appropriate.
+  virtual Value* Deserialize(int* error_code, std::string* error_str) = 0;
 };
 
 #endif  // BASE_VALUES_H_