Convert some GN test support targets to static libs.

components/syncable_prefs/BUILD.gn

 # Copyright 2015 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")
 
-source_set("syncable_prefs") {
+static_library("syncable_prefs") {
   sources = [
     "pref_model_associator.cc",
     "pref_model_associator.h",
     "pref_model_associator_client.h",
     "pref_service_syncable.cc",
     "pref_service_syncable.h",
     "pref_service_syncable_factory.cc",
     "pref_service_syncable_factory.h",
     "pref_service_syncable_observer.h",
     "synced_pref_change_registrar.cc",
@@ skipping 12 matching lines @@
     # This define is only used for compiling the .cc files in this target.
     defines = [ "SYNCABLE_PREFS_USE_POLICY" ]
 
     deps += [
       "//components/policy:policy_component_browser",
       "//components/policy:policy_component_common",
     ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "pref_service_mock_factory.cc",
     "pref_service_mock_factory.h",
     "testing_pref_service_syncable.cc",
     "testing_pref_service_syncable.h",
   ]
 
   deps = [
     ":syncable_prefs",
@@ skipping 13 matching lines @@
 
   deps = [
     ":syncable_prefs",
     ":test_support",
     "//components/pref_registry",
     "//components/prefs",
     "//sync:test_support_sync_api",
     "//testing/gtest",
   ]
 }