[Sync] Add support for automatic enabling of syncing tab favicons.

chrome/browser/sync/profile_sync_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 "chrome/browser/sync/profile_sync_service.h"
 
 #include <cstddef>
 #include <map>
 #include <set>
 #include <utility>
@@ skipping 43 matching lines @@
 #include "chrome/common/time_format.h"
 #include "chrome/common/url_constants.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 #include "grit/generated_resources.h"
 #include "net/cookies/cookie_monster.h"
 #include "sync/internal_api/configure_reason.h"
 #include "sync/js/js_arg_list.h"
 #include "sync/js/js_event_details.h"
 #include "sync/util/cryptographer.h"
+#include "sync/util/experiments.h"
 #include "ui/base/l10n/l10n_util.h"
 
 using browser_sync::ChangeProcessor;
 using browser_sync::DataTypeController;
 using browser_sync::DataTypeManager;
 using browser_sync::JsBackend;
 using browser_sync::JsController;
 using browser_sync::JsEventDetails;
 using browser_sync::JsEventHandler;
 using browser_sync::SyncBackendHost;
@@ skipping 626 matching lines @@
     // server time as last reported by CheckServerReachable, so we don't have to
     // rely on the local clock, which may be off significantly.
     MessageLoop::current()->PostTask(FROM_HERE,
         base::Bind(&browser_sync::SessionModelAssociator::DeleteStaleSessions,
                    GetSessionModelAssociator()->AsWeakPtr()));
   }
   DVLOG(2) << "Notifying observers sync cycle completed";
   NotifyObservers();
 }
 
-// TODO(sync): eventually support removing datatypes too.
-void ProfileSyncService::OnDataTypesChanged(
-    syncable::ModelTypeSet to_add) {
+void ProfileSyncService::OnExperimentsChanged(
+    const browser_sync::Experiments& experiments) {
+  if (current_experiments.Matches(experiments))
+    return;
+
   // If this is a first time sync for a client, this will be called before
   // OnBackendInitialized() to ensure the new datatypes are available at sync
   // setup. As a result, the migrator won't exist yet. This is fine because for
   // first time sync cases we're only concerned with making the datatype
   // available.
   if (migrator_.get() &&
       migrator_->state() != browser_sync::BackendMigrator::IDLE) {
-    DVLOG(1) << "Dropping OnDataTypesChanged due to migrator busy.";
+    DVLOG(1) << "Dropping OnExperimentsChanged due to migrator busy.";
     return;
   }
 
-  DVLOG(2) << "OnDataTypesChanged called with types: "
-           << syncable::ModelTypeSetToString(to_add);
-
   const syncable::ModelTypeSet registered_types = GetRegisteredDataTypes();
-
+  syncable::ModelTypeSet to_add;
+  if (experiments.sync_tabs)
+    to_add.Put(syncable::SESSIONS);
   const syncable::ModelTypeSet to_register =
       Difference(to_add, registered_types);
-
+  DVLOG(2) << "OnExperimentsChanged called with types: "
+           << syncable::ModelTypeSetToString(to_add);
   DVLOG(2) << "Enabling types: " << syncable::ModelTypeSetToString(to_register);
 
   for (syncable::ModelTypeSet::Iterator it = to_register.First();
        it.Good(); it.Inc()) {
     // Received notice to enable experimental type. Check if the type is
     // registered, and if not register a new datatype controller.
     RegisterNewDataType(it.Get());
 #if !defined(OS_ANDROID)
     // Enable the about:flags switch for the experimental type so we don't have
     // to always perform this reconfiguration. Once we set this, the type will
@@ skipping 19 matching lines @@
     sync_prefs_.SetPreferredDataTypes(registered_types, registered_types);
 
     // Only automatically turn on types if we have already finished set up.
     // Otherwise, just leave the experimental types on by default.
     if (!to_register.Empty() && HasSyncSetupCompleted() && migrator_.get()) {
       DVLOG(1) << "Dynamically enabling new datatypes: "
                << syncable::ModelTypeSetToString(to_register);
       OnMigrationNeededForTypes(to_register);
     }
   }
+
+  // Now enable any non-datatype features.
+  if (experiments.sync_tab_favicons) {
+    DVLOG(1) << "Enabling syncing of tab favicons.";
+    about_flags::SetExperimentEnabled(g_browser_process->local_state(),
+                                      "sync-tab-favicons",
+                                      true);
+  }
+
+  current_experiments = experiments;
 }
 
 void ProfileSyncService::UpdateAuthErrorState(
     const GoogleServiceAuthError& error) {
   is_auth_in_progress_ = false;
   last_auth_error_ = error;
 
   // Fan the notification out to interested UI-thread components.
   NotifyObservers();
 }
@@ skipping 861 matching lines @@
   // See http://stackoverflow.com/questions/6224121/is-new-this-myclass-undefined-behaviour-after-directly-calling-the-destru.
   ProfileSyncService* old_this = this;
   this->~ProfileSyncService();
   new(old_this) ProfileSyncService(
       new ProfileSyncComponentsFactoryImpl(profile,
                                            CommandLine::ForCurrentProcess()),
       profile,
       signin,
       behavior);
 }