Disable sync for Lightspeed experimentation.

chrome/browser/sync/profile_sync_components_factory_impl.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 "base/command_line.h"
 #include "build/build_config.h"
 #include "chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "chrome/browser/bookmarks/enhanced_bookmarks_features.h"
 #include "chrome/browser/dom_distiller/dom_distiller_service_factory.h"
 #include "chrome/browser/history/history_service.h"
@@ skipping 128 matching lines @@
 using sync_driver::SharedChangeProcessor;
 using sync_driver::UIDataTypeController;
 
 namespace {
 
 syncer::ModelTypeSet GetDisabledTypesFromCommandLine(
     const base::CommandLine& command_line) {
   syncer::ModelTypeSet disabled_types;
   std::string disabled_types_str =
       command_line.GetSwitchValueASCII(switches::kDisableSyncTypes);
+
+  // Disable sync types experimentally to measure impact on startup time.
+  // TODO(mlerman): Remove this after the experiment. crbug.com/454788
+  std::string disable_types_finch =
+      variations::GetVariationParamValue("LightSpeed", "DisableSyncPart");
+  if (!disable_types_finch.empty()) {
+    if (disabled_types_str.empty())
+      disabled_types_str = disable_types_finch;
+    else
+      disabled_types_str += ", " + disable_types_finch;
+  }
+
   disabled_types = syncer::ModelTypeSetFromString(disabled_types_str);
   return disabled_types;
 }
 
 syncer::ModelTypeSet GetEnabledTypesFromCommandLine(
     const base::CommandLine& command_line) {
   syncer::ModelTypeSet enabled_types;
   return enabled_types;
 }
 
@@ skipping 558 matching lines @@
       new TypedUrlModelAssociator(profile_sync_service,
                                   history_backend,
                                   error_handler);
   TypedUrlChangeProcessor* change_processor =
       new TypedUrlChangeProcessor(profile_,
                                   model_associator,
                                   history_backend,
                                   error_handler);
   return SyncComponents(model_associator, change_processor);
 }