[WIP][Base] Use variadic template for Callback and Bind

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 97 matching lines @@
     "bind_internal.h",
     "bind_internal_win.h",
     "bits.h",
     "build_time.cc",
     "build_time.h",
     "callback.h",
     "callback_helpers.cc",
     "callback_helpers.h",
     "callback_internal.cc",
     "callback_internal.h",
+    "callback_tuple.h",
     "cancelable_callback.h",
     "command_line.cc",
     "command_line.h",
     "compiler_specific.h",
     "containers/adapters.h",
     "containers/hash_tables.h",
     "containers/linked_list.h",
     "containers/mru_cache.h",
     "containers/small_map.h",
     "containers/stack_container.h",
@@ skipping 1361 matching lines @@
   # GYP: //base.gyp:base_unittests_apk
   unittest_apk("base_unittests_apk") {
     deps = [
       ":base_java",
       ":base_java_unittest_support",
       ":base_unittests",
     ]
     unittests_dep = ":base_unittests"
   }
 }