Preference provider implementation backed by JSON files in a directory.

base/values.h

Index: base/values.h
diff --git a/base/values.h b/base/values.h
index 248fc1d6e9d65620cd32d797964b91bb340b2f95..5c0ea336101323166057531827db23f24ae17e47 100644
--- a/base/values.h
+++ b/base/values.h
@@ -312,6 +312,12 @@ class DictionaryValue : public Value {
   // the copy.  This never returns NULL, even if |this| itself is empty.
   DictionaryValue* DeepCopyWithoutEmptyChildren();
 
+  // Merge a given dictionary into this dictionary. This is done recursively,
+  // i.e. any subdictionaries will be merged as well. In case of key collisions,
+  // the passed in dictionary takes precedence and data already present will be
+  // replaced.
+  void MergeDictionary(const DictionaryValue* dictionary);
+
   // This class provides an iterator for the keys in the dictionary.
   // It can't be used to modify the dictionary.
   //