scheduler: Start running WebThread unit tests again

Looks like these were accidentally removed when the scheduler was turned into
a component.

BUG=477690

Review URL: https://codereview.chromium.org/1112523003

Cr-Commit-Position: refs/heads/master@{#327271}

components/components_tests.gyp

@@ -442,9 +442,11 @@
       'scheduler/child/task_queue_manager_unittest.cc',
       'scheduler/child/test_time_source.cc',
       'scheduler/child/test_time_source.h',
+      'scheduler/child/webthread_impl_for_worker_scheduler_unittest.cc',
       'scheduler/child/worker_scheduler_impl_unittest.cc',
       'scheduler/renderer/deadline_task_runner_unittest.cc',
       'scheduler/renderer/renderer_scheduler_impl_unittest.cc',
+      'scheduler/renderer/webthread_impl_for_renderer_scheduler_unittest.cc',
     ],
     'search_unittest_sources': [
       'search/search_android_unittest.cc',

components/scheduler/BUILD.gn

@@ -42,9 +42,11 @@ source_set("unit_tests") {
     "child/task_queue_manager_unittest.cc",
     "child/test_time_source.cc",
     "child/test_time_source.h",
+    "child/webthread_impl_for_worker_scheduler_unittest.cc",
     "child/worker_scheduler_impl_unittest.cc",
     "renderer/deadline_task_runner_unittest.cc",
     "renderer/renderer_scheduler_impl_unittest.cc",
+    "renderer/webthread_impl_for_renderer_scheduler_unittest.cc",
   ]
 
   deps = [