[Sync] Add support for enabling session sync remotely.

chrome/browser/sync/glue/sync_backend_host.cc

 // Copyright (c) 2011 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 "build/build_config.h"
 
 #include <algorithm>
 #include <map>
 
 #include "base/bind.h"
@@ skipping 849 matching lines @@
     return;
   DCHECK_EQ(MessageLoop::current(), host_->frontend_loop_);
 
   host_->last_snapshot_.reset(snapshot);
 
   const syncable::ModelTypeSet& to_migrate =
       snapshot->syncer_status.types_needing_local_migration;
   if (!to_migrate.empty())
     host_->frontend_->OnMigrationNeededForTypes(to_migrate);
 
+  // Process any changes to the datatypes we're syncing.
+  // TODO(sync): add support for removing types.
+  syncable::ModelTypeSet to_add;
+  if (sync_manager()->ReceivedExperimentalTypes(&to_add) &&
+      host_->initialized()) {
+    host_->frontend_->OnDataTypesChanged(to_add);
+  }
+
   // If we are waiting for a configuration change, check here to see
   // if this sync cycle has initialized all of the types we've been
   // waiting for.
   if (host_->pending_download_state_.get()) {
     scoped_ptr<PendingConfigureDataTypesState> state(
         host_->pending_download_state_.release());
     DCHECK(
         std::includes(state->types_to_add.begin(), state->types_to_add.end(),
                       state->added_types.begin(), state->added_types.end()));
     syncable::ModelTypeBitSet added_types =
@@ skipping 181 matching lines @@
 }
 
 void SyncBackendHost::Core::DeleteSyncDataFolder() {
   if (file_util::DirectoryExists(host_->sync_data_folder_path())) {
     if (!file_util::Delete(host_->sync_data_folder_path(), true))
       LOG(DFATAL) << "Could not delete the Sync Data folder.";
   }
 }
 
 }  // namespace browser_sync