Pref service: Add a ScopedDictionaryPrefUpdate to track value changes.

components/prefs/pref_service.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 "components/prefs/pref_service.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 474 matching lines @@
                                        GetWriteFlags(pref));
   }
   return value;
 }
 
 void PrefService::ReportUserPrefChanged(const std::string& key) {
   DCHECK(CalledOnValidThread());
   user_pref_store_->ReportValueChanged(key, GetWriteFlags(FindPreference(key)));
 }
 
+void PrefService::ReportUserPrefChanged(
+    const std::string& key,
+    std::set<std::vector<std::string>> path_components) {
+  DCHECK(CalledOnValidThread());
+  user_pref_store_->ReportSubValuesChanged(key, std::move(path_components),
+                                           GetWriteFlags(FindPreference(key)));
+}
+
 void PrefService::SetUserPrefValue(const std::string& path,
                                    std::unique_ptr<base::Value> new_value) {
   DCHECK(CalledOnValidThread());
 
   const Preference* pref = FindPreference(path);
   if (!pref) {
     NOTREACHED() << "Trying to write an unregistered pref: " << path;
     return;
   }
   if (pref->GetType() != new_value->GetType()) {
@@ skipping 110 matching lines @@
       DCHECK(found_value->IsType(default_type));
       return found_value;
     } else {
       // Every registered preference has at least a default value.
       NOTREACHED() << "no valid value found for registered pref " << path;
     }
   }
 
   return NULL;
 }