Remove JsonPrefStore pruning of empty values on write.

base/prefs/pref_registry.cc

 // 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.
 
 #include "base/prefs/pref_registry.h"
 
 #include "base/logging.h"
 #include "base/prefs/default_pref_store.h"
 #include "base/prefs/pref_store.h"
 #include "base/values.h"
@@ skipping 24 matching lines @@
     const base::Value* current_value = NULL;
     DCHECK(defaults_->GetValue(pref_name, &current_value))
         << "Setting default for unregistered pref: " << pref_name;
     DCHECK(value->IsType(current_value->GetType()))
         << "Wrong type for new default: " << pref_name;
   }
 
   defaults_->ReplaceDefaultValue(pref_name, make_scoped_ptr(value));
 }
 
-void PrefRegistry::SetRegistrationCallback(
-    const RegistrationCallback& callback) {
-  registration_callback_ = callback;
-}
-
 void PrefRegistry::RegisterPreference(const char* path,
                                       base::Value* default_value) {
   base::Value::Type orig_type = default_value->GetType();
   DCHECK(orig_type != base::Value::TYPE_NULL &&
          orig_type != base::Value::TYPE_BINARY) <<
          "invalid preference type: " << orig_type;
   DCHECK(!defaults_->GetValue(path, NULL)) <<
       "Trying to register a previously registered pref: " << path;
 
   defaults_->SetDefaultValue(path, make_scoped_ptr(default_value));
-
-  if (!registration_callback_.is_null())
-    registration_callback_.Run(path, default_value);
 }