Invoke the StartSyncFlare for prefs when performing an automatic reset.

chrome/browser/prefs/profile_pref_store_manager.cc

 // Copyright 2014 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/profile_pref_store_manager.h"
 
 #include "base/bind.h"
+#include "base/callback.h"
 #include "base/file_util.h"
 #include "base/json/json_file_value_serializer.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/prefs/json_pref_store.h"
 #include "base/prefs/persistent_pref_store.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "chrome/browser/prefs/pref_hash_store_impl.h"
 #include "chrome/browser/prefs/tracked/pref_service_hash_store_contents.h"
 #include "chrome/browser/prefs/tracked/segregated_pref_store.h"
 #include "chrome/browser/prefs/tracked/tracked_preferences_migration.h"
+#include "chrome/browser/sync/glue/sync_start_util.h"
 #include "chrome/common/chrome_constants.h"
 #include "chrome/common/pref_names.h"
 #include "components/pref_registry/pref_registry_syncable.h"
+#include "sync/internal_api/public/base/model_type.h"
 
 // TODO(erikwright): Enable this on Chrome OS and Android once MACs are moved
 // out of Local State. This will resolve a race condition on Android and a
 // privacy issue on ChromeOS. http://crbug.com/349158
 const bool ProfilePrefStoreManager::kPlatformSupportsPreferenceTracking =
 #if defined(OS_ANDROID) || defined(OS_CHROMEOS)
     false;
 #else
     true;
 #endif
@@ skipping 69 matching lines @@
        ++it) {
     if (it->enforcement_level > PrefHashFilter::NO_ENFORCEMENT) {
       protected_configuration.push_back(*it);
       protected_pref_names.insert(it->name);
     } else {
       unprotected_configuration.push_back(*it);
       unprotected_pref_names.insert(it->name);
     }
   }
 
+  // Used to kick sync early in case of a reset event. This is done since sync
+  // may bring back the user's server value post-reset which could potentially
+  // cause a "settings flash" between the factory default and the
+  // re-instantiated server value. Starting sync ASAP minimizes the window
+  // before the server value is re-instantiated (this window can otherwise be
+  // as long as 10 seconds by default).
+  const base::Closure start_sync_flare_for_prefs =

[erikwright (departed), 2014/07/16 20:23:43]

This should be a dependency passed in by chrome_pref_service_factory, not a
static access in this class. That will be much more testable.

[gab, 2014/07/16 20:30:39]

How is it more testable? I thought about it, but I'm not sure that another layer
of piping gives us anything here... The |on_reset| callback is already tested in
pref_hash_filter_unittest.cc; testing that the flare itself is called would
likely require a huge test (involving services et al.) and I'm not convinced
that's truly required for such a simple hook.

+      base::Bind(sync_start_util::GetFlareForSyncableService(profile_path_),
+                 syncer::PREFERENCES);
+
   scoped_ptr<PrefHashFilter> unprotected_pref_hash_filter(
       new PrefHashFilter(GetPrefHashStore(false),
                          unprotected_configuration,
+                         base::Closure(),
                          validation_delegate,
                          reporting_ids_count_,
                          false));
   scoped_ptr<PrefHashFilter> protected_pref_hash_filter(
       new PrefHashFilter(GetPrefHashStore(true),
                          protected_configuration,
+                         start_sync_flare_for_prefs,
                          validation_delegate,
                          reporting_ids_count_,
                          true));
 
   PrefHashFilter* raw_unprotected_pref_hash_filter =
       unprotected_pref_hash_filter.get();
   PrefHashFilter* raw_protected_pref_hash_filter =
       protected_pref_hash_filter.get();
 
   scoped_refptr<JsonPrefStore> unprotected_pref_store(
@@ skipping 38 matching lines @@
     return false;
 
   const base::DictionaryValue* to_serialize = &master_prefs;
   scoped_ptr<base::DictionaryValue> copy;
 
   if (kPlatformSupportsPreferenceTracking) {
     copy.reset(master_prefs.DeepCopy());
     to_serialize = copy.get();
     PrefHashFilter(GetPrefHashStore(false),
                    tracking_configuration_,
+                   base::Closure(),
                    NULL,
                    reporting_ids_count_,
                    false).Initialize(copy.get());
   }
 
   // This will write out to a single combined file which will be immediately
   // migrated to two files on load.
   JSONFileValueSerializer serializer(
       GetPrefFilePathFromProfilePath(profile_path_));
 
@@ skipping 14 matching lines @@
   scoped_ptr<PrefFilter> pref_filter;
   if (kPlatformSupportsPreferenceTracking) {
     scoped_ptr<PrefHashStoreImpl> pref_hash_store_impl(
         new PrefHashStoreImpl(seed_, device_id_, true));
     pref_hash_store_impl->set_legacy_hash_store_contents(
         scoped_ptr<HashStoreContents>(new PrefServiceHashStoreContents(
             profile_path_.AsUTF8Unsafe(), local_state_)));
     pref_filter.reset(
         new PrefHashFilter(pref_hash_store_impl.PassAs<PrefHashStore>(),
                            tracking_configuration_,
+                           base::Closure(),
                            NULL,
                            reporting_ids_count_,
                            false));
   }
   return new JsonPrefStore(GetPrefFilePathFromProfilePath(profile_path_),
                            io_task_runner,
                            pref_filter.Pass());
 }
 
 scoped_ptr<PrefHashStore> ProfilePrefStoreManager::GetPrefHashStore(
     bool use_super_mac) {
   DCHECK(kPlatformSupportsPreferenceTracking);
 
   return scoped_ptr<PrefHashStore>(new PrefHashStoreImpl(
       seed_,
       device_id_,
       use_super_mac));
 }