scheduler: Add a missing unit test to BUILD.gn

components/scheduler/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("//components/scheduler/scheduler.gni")
 
 # GYP version: components/scheduler.gypi:scheduler
 component("scheduler") {
   sources = rebase_path(scheduler_gypi_values.scheduler_sources,
                         ".",
@@ skipping 21 matching lines @@
 source_set("common") {
   sources = rebase_path(scheduler_gypi_values.scheduler_common_sources,
                         ".",
                         "//components/scheduler")
 }
 
 source_set("unit_tests") {
   testonly = true
 
   sources = [
+    "child/idle_helper_unittest.cc",
     "child/nestable_task_runner_for_test.cc",
     "child/nestable_task_runner_for_test.h",
     "child/prioritizing_task_queue_selector_unittest.cc",
     "child/scheduler_helper_unittest.cc",
     "child/scheduler_task_runner_delegate_for_test.cc",
     "child/scheduler_task_runner_delegate_for_test.h",
     "child/scheduler_task_runner_delegate_impl_unittest.cc",
     "child/task_queue_manager_unittest.cc",
     "child/test_time_source.cc",
     "child/test_time_source.h",
@@ skipping 17 matching lines @@
 # GYP version: components/scheduler.gypi:scheduler_test_support
 static_library("test_support") {
   sources = rebase_path(scheduler_gypi_values.scheduler_test_support_sources,
                         ".",
                         "//components/scheduler")
 
   deps = [
     "//base",
   ]
 }