use variadic macros/templates in IPC message implementation

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.
 
 # HOW TO WRITE CONDITIONALS IN THIS FILE
 # ======================================
 #
 # In many other places, one would write a conditional that expresses all the
 # cases when a source file is used or unused, and then either add or subtract
 # it from the sources list in that case
@@ skipping 258 matching lines @@
     "debug/stack_trace.h",
     "debug/stack_trace_android.cc",
     "debug/stack_trace_posix.cc",
     "debug/stack_trace_win.cc",
     "debug/task_annotator.cc",
     "debug/task_annotator.h",
     "deferred_sequenced_task_runner.cc",
     "deferred_sequenced_task_runner.h",
     "environment.cc",
     "environment.h",
+    "export_template.h",
     "feature_list.cc",
     "feature_list.h",
     "file_descriptor_posix.h",
     "file_version_info.h",
     "file_version_info_mac.h",
     "file_version_info_mac.mm",
     "file_version_info_win.cc",
     "file_version_info_win.h",
     "files/dir_reader_fallback.h",
     "files/dir_reader_linux.h",
@@ skipping 1858 matching lines @@
 
   # GYP: //base.gyp:base_java_unittest_support
   android_library("base_java_unittest_support") {
     deps = [
       ":base_java",
     ]
     java_files =
         [ "test/android/java/src/org/chromium/base/ContentUriTestUtils.java" ]
   }
 }