Componentize more signin code

components/signin/core/browser/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.
 
 static_library("browser") {
   sources = [
     "about_signin_internals.cc",
     "about_signin_internals.h",
     "account_fetcher_service.cc",
     "account_fetcher_service.h",
@@ skipping 58 matching lines @@
   if (is_chromeos) {
     sources -= [ "signin_manager.cc" ]
   }
 }
 
 static_library("test_support") {
   testonly = true
   sources = [
     "fake_auth_status_provider.cc",
     "fake_auth_status_provider.h",
+    "fake_profile_oauth2_token_service.cc",
+    "fake_profile_oauth2_token_service.h",
     "test_signin_client.cc",
     "test_signin_client.h",
   ]
 
   deps = [
     ":browser",
     "//testing/gtest",
   ]
 }