Introduce TaskRunnerHandle.

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 804 matching lines @@
     "threading/platform_thread_posix.cc",
     "threading/platform_thread_win.cc",
     "threading/post_task_and_reply_impl.cc",
     "threading/post_task_and_reply_impl.h",
     "threading/sequenced_task_runner_handle.cc",
     "threading/sequenced_task_runner_handle.h",
     "threading/sequenced_worker_pool.cc",
     "threading/sequenced_worker_pool.h",
     "threading/simple_thread.cc",
     "threading/simple_thread.h",
+    "threading/task_runner_handle.cc",

[fdoray, 2016/06/17 14:29:01]

Why is this in base/threading/? Could it be in base/ like task_runner.h? Or
could we move this, task_runner.h and (sequenced|single_thread)_task_runner.h in
base/task/?

IMO, base/threading/ should be only for:
- Managing threads and their properties (platform_thread.h, simple_thread.h,
sequenced_worker_pool.h, thread_id_name_manager.h, ...)
- Providing access to thread-local storage (thread_local.h, ...)
- Verifying that code runs on the appropriate thread (non_thread_safe.h,
thread_restrictions.h, ...)

[gab, 2016/06/20 19:55:35]

I agree that this is weird, I had the same thought multiple times (I hate that
task_runners are in base/ root and also find it weird for the
task_runner_handles to be in base/threading/.

If we introduce something like base/task, maybe we could put post_task.h in it
as well? Keeping base/task_scheduler for the implementation? Do you want to kick
off a discussion on this in a bug with base/ OWNERS?

+    "threading/task_runner_handle.h",
+    "threading/task_runner_handle_internal.h",
     "threading/thread.cc",
     "threading/thread.h",
     "threading/thread_checker.h",
     "threading/thread_checker_impl.cc",
     "threading/thread_checker_impl.h",
     "threading/thread_collision_warner.cc",
     "threading/thread_collision_warner.h",
     "threading/thread_id_name_manager.cc",
     "threading/thread_id_name_manager.h",
     "threading/thread_local.h",
@@ skipping 1054 matching lines @@
     "test/icu_test_util.h",
     "test/test_pending_task_unittest.cc",
     "test/test_reg_util_win_unittest.cc",
     "test/trace_event_analyzer_unittest.cc",
     "test/user_action_tester_unittest.cc",
     "threading/non_thread_safe_unittest.cc",
     "threading/platform_thread_unittest.cc",
     "threading/sequenced_task_runner_handle_unittest.cc",
     "threading/sequenced_worker_pool_unittest.cc",
     "threading/simple_thread_unittest.cc",
+    "threading/task_runner_handle_unittest.cc",
     "threading/thread_checker_unittest.cc",
     "threading/thread_collision_warner_unittest.cc",
     "threading/thread_id_name_manager_unittest.cc",
     "threading/thread_local_storage_unittest.cc",
     "threading/thread_local_unittest.cc",
     "threading/thread_unittest.cc",
     "threading/watchdog_unittest.cc",
     "threading/worker_pool_posix_unittest.cc",
     "threading/worker_pool_unittest.cc",
     "time/pr_time_unittest.cc",
@@ skipping 482 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" ]
   }
 }