Remove JsonPrefStore pruning of empty values on write.

base/values.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.
 
 // This file specifies a recursive data storage class called Value intended for
 // storing settings and other persistable data.
 //
 // A Value represents something that can be stored in JSON or passed to/from
 // JavaScript. As such, it is NOT a generalized variant type, since only the
 // types supported by JavaScript/JSON are supported.
@@ skipping 306 matching lines @@
   // |out_value|.  If |out_value| is NULL, the removed value will be deleted.
   // This method returns true if |path| is a valid path; otherwise it will
   // return false and the DictionaryValue object will be unchanged.
   virtual bool Remove(const std::string& path, scoped_ptr<Value>* out_value);
 
   // Like Remove(), but without special treatment of '.'.  This allows e.g. URLs
   // to be used as paths.
   virtual bool RemoveWithoutPathExpansion(const std::string& key,
                                           scoped_ptr<Value>* out_value);
 
+  // Removes a path, clearing out all dictionaries on |path| that remain empty
+  // after removing the value at |path|.
+  virtual bool RemovePath(const std::string& path,
+                          scoped_ptr<Value>* out_value);
+
   // Makes a copy of |this| but doesn't include empty dictionaries and lists in
   // the copy.  This never returns NULL, even if |this| itself is empty.
   DictionaryValue* DeepCopyWithoutEmptyChildren() const;
 
   // Merge |dictionary| into this dictionary. This is done recursively, i.e. any
   // sub-dictionaries will be merged as well. In case of key collisions, the
   // passed in dictionary takes precedence and data already present will be
   // replaced. Values within |dictionary| are deep-copied, so |dictionary| may
   // be freed any time after this call.
   void MergeDictionary(const DictionaryValue* dictionary);
@@ skipping 185 matching lines @@
 
 }  // namespace base
 
 // http://crbug.com/88666
 using base::DictionaryValue;
 using base::ListValue;
 using base::StringValue;
 using base::Value;
 
 #endif  // BASE_VALUES_H_