Remove JsonPrefStore pruning of empty values on write.

chrome/browser/prefs/pref_metrics_service.cc

 // Copyright 2013 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 "chrome/browser/prefs/pref_metrics_service.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/json/json_string_value_serializer.h"
 #include "base/metrics/histogram.h"
@@ skipping 281 matching lines @@
   // Get the hashed prefs dictionary if it exists. If it doesn't, it will be
   // created if we set preference values below.
   const base::DictionaryValue* hashed_prefs = NULL;
   pref_hash_dicts->GetDictionaryWithoutPathExpansion(profile_name_,
                                                      &hashed_prefs);
   for (int i = 0; i < tracked_pref_path_count_; ++i) {
     // Skip prefs that haven't been registered.
     if (!prefs_->FindPreference(tracked_pref_paths_[i]))
       continue;
 
-    // Make sure tracked prefs are saved to disk even if empty.
-    // TODO(gab): Guarantee this for all prefs at a lower level and remove this
-    // hack.
-    prefs_->MarkUserStoreNeedsEmptyValue(tracked_pref_paths_[i]);
-
     const base::Value* value = prefs_->GetUserPrefValue(tracked_pref_paths_[i]);
     std::string last_hash;
     // First try to get the stored expected hash...
     if (hashed_prefs &&
         hashed_prefs->GetString(tracked_pref_paths_[i], &last_hash)) {
       // ... if we have one get the hash of the current value...
       const std::string value_hash =
           GetHashedPrefValue(tracked_pref_paths_[i], value,
                              HASHED_PREF_STYLE_NEW);
       // ... and check that it matches...
@@ skipping 148 matching lines @@
 }
 
 bool PrefMetricsService::Factory::ServiceIsNULLWhileTesting() const {
   return false;
 }
 
 content::BrowserContext* PrefMetricsService::Factory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }