[Startup Tracing] Enable startup tracing from config file

components/BUILD.gn

 # 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.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//tools/grit/repack.gni")
 
 # Collection of all components. You wouldn't link to this, but this is rather
@@ skipping 80 matching lines @@
     "//components/resources:components_resources",
     "//components/search",
     "//components/search_engines",
     "//components/search_provider_logos",
     "//components/sessions",
     "//components/signin/core/browser",
     "//components/startup_metric_utils",
     "//components/strings",
     "//components/sync_driver",
     "//components/tracing",
+    "//components/tracing:startup_tracing",
     "//components/translate/content/browser",
     "//components/translate/content/common",
     "//components/translate/content/renderer",
     "//components/translate/core/browser",
     "//components/translate/core/common",
     "//components/ui/zoom:ui_zoom",
     "//components/undo",
     "//components/update_client",
     "//components/url_fixer",
     "//components/url_matcher",
@@ skipping 313 matching lines @@
 
   deps = [
     "//base",
     "//base/test:test_support_perf",
     "//testing/gtest",
     "//testing/perf",
     "//content/test:test_support",
     "//components/visitedlink/browser",
   ]
 }