Convert some GN test support targets to static libs.

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.
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
-source_set("browser") {
+static_library("browser") {
   sources = [
     "about_signin_internals.cc",
     "about_signin_internals.h",
     "account_fetcher_service.cc",
     "account_fetcher_service.h",
     "account_info.cc",
     "account_info.h",
     "account_info_fetcher.cc",
     "account_info_fetcher.h",
     "account_investigator.cc",
@@ skipping 86 matching lines @@
 
   if (is_android) {
     sources -= [
       "child_account_info_fetcher_impl.cc",
       "child_account_info_fetcher_impl.h",
     ]
     deps += [ "android:jni_headers" ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "fake_account_fetcher_service.cc",
     "fake_account_fetcher_service.h",
     "fake_auth_status_provider.cc",
     "fake_auth_status_provider.h",
     "fake_gaia_cookie_manager_service.cc",
     "fake_gaia_cookie_manager_service.h",
     "fake_profile_oauth2_token_service.cc",
     "fake_profile_oauth2_token_service.h",
@@ skipping 45 matching lines @@
 }
 
 if (is_android) {
   # GYP: //component/signin.gypi:investigated_scenario_java
   java_cpp_enum("investigated_scenario_java") {
     sources = [
       "signin_investigator.h",
     ]
   }
 }