Split testing_pref_service.h/.cc into two parts, generic vs. Chrome-specific.

chrome/chrome_tests_unit.gypi

Index: chrome/chrome_tests_unit.gypi
diff --git a/chrome/chrome_tests_unit.gypi b/chrome/chrome_tests_unit.gypi
index c377966527480957fb3483a20ee7fafc669cb5e3..d547f0fad26eda93f69141e733c138300b8d40c1 100644
--- a/chrome/chrome_tests_unit.gypi
+++ b/chrome/chrome_tests_unit.gypi
@@ -218,6 +218,8 @@
         'test/base/module_system_test.h',
         'test/base/profile_mock.cc',
         'test/base/profile_mock.h',
+        'test/base/scoped_testing_local_state.cc',
+        'test/base/scoped_testing_local_state.h',
         'test/base/test_browser_window.cc',
         'test/base/test_browser_window.h',
         'test/base/test_launcher_utils.cc',
@@ -230,6 +232,8 @@
         'test/base/testing_browser_process.h',
         'test/base/testing_pref_service.cc',
         'test/base/testing_pref_service.h',
+        'test/base/testing_pref_service_syncable.cc',
+        'test/base/testing_pref_service_syncable.h',
         'test/base/testing_profile.cc',
         'test/base/testing_profile.h',
         'test/base/testing_profile_manager.cc',