Split ios/chrome/app/startup targets to reduce dependencies.

ios/clean/chrome/app/steps/BUILD.gn

 # Copyright 2016 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.
 
 source_set("steps") {
   sources = [
     "launch_to_background.h",
     "launch_to_background.mm",
     "launch_to_basic.h",
     "launch_to_basic.mm",
     "launch_to_foreground.h",
     "launch_to_foreground.mm",
     "root_coordinator+application_step.h",
     "root_coordinator+application_step.mm",
   ]
 
   configs += [ "//build/config/compiler:enable_arc" ]
 
   deps = [
     "//base",
     "//components/content_settings/core/browser",
     "//ios/chrome/app:app_internal",
     "//ios/chrome/app/startup",
+    "//ios/chrome/app/startup:startup_basic",
     "//ios/chrome/browser",
     "//ios/chrome/browser:browser_internal",
     "//ios/chrome/browser/browser_state",
     "//ios/chrome/browser/browser_state:browser_state_impl",
     "//ios/chrome/browser/content_settings",
     "//ios/chrome/browser/web:web_internal",
     "//ios/chrome/browser/web_state_list",
     "//ios/clean/chrome/app:application_state",
     "//ios/clean/chrome/browser/ui/root",
     "//ios/net",
@@ skipping 13 matching lines @@
   configs += [ "//build/config/compiler:enable_arc" ]
 
   deps = [
     ":steps",
     "//base",
     "//ios/clean/chrome/app:application_state",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 }