Convert some GN test support targets to static libs.

components/user_prefs/tracked/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("user_prefs_tracked") {
   sources = [
     "device_id.h",
     "device_id_mac.cc",
     "device_id_stub.cc",
     "device_id_win.cc",
@@ skipping 38 matching lines @@
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   deps = [
     "//base:base",
     "//components/pref_registry",
     "//components/prefs",
     "//crypto:crypto",
   ]
 }
 
-source_set("user_prefs_tracked_test_support") {
+static_library("user_prefs_tracked_test_support") {
   testonly = true
   sources = [
     "mock_validation_delegate.cc",
     "mock_validation_delegate.h",
   ]
 
   deps = [
     ":user_prefs_tracked",
     "//base:base",
   ]
@@ skipping 12 matching lines @@
   ]
 
   deps = [
     ":user_prefs_tracked",
     ":user_prefs_tracked_test_support",
     "//base:base",
     "//components/prefs:test_support",
     "//testing/gtest",
   ]
 }