Refactor GN source expansions.

base/BUILD.gn

 # Copyright (c) 2013 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/ui.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
@@ skipping 153 matching lines @@
     "debug/trace_event_synthetic_delay.cc",
     "debug/trace_event_synthetic_delay.h",
     "debug/trace_event_system_stats_monitor.cc",
     "debug/trace_event_system_stats_monitor.h",
     "debug/trace_event_win.cc",
     "deferred_sequenced_task_runner.cc",
     "deferred_sequenced_task_runner.h",
     "environment.cc",
     "environment.h",
     "event_recorder.h",
-    "event_recorder_stubs.cc",
     "event_recorder_win.cc",
     "file_descriptor_posix.h",
     "file_util.cc",
     "file_util.h",
     "file_util_android.cc",
     "file_util_linux.cc",
     "file_util_mac.mm",
     "file_util_posix.cc",
     "file_util_win.cc",
     "file_version_info.h",
@@ skipping 1264 matching lines @@
 
   unittest_apk("base_unittests_apk") {
     deps = [
       ":base_java",
       ":base_java_unittest_support",
       ":base_unittests",
     ]
     unittests_dep = ":base_unittests"
   }
 }