Make new TaskRunner, SequencedTaskRunner, and SingleThreadTaskRunner interfaces

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index 36400ede21bb17ff9ac306bf97258c3bf30ac79a..693f393fb91ee791a4c911e53d59c0a47f3ab1a2 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -187,6 +187,7 @@
           'memory/weak_ptr.h',
           'message_loop.cc',
           'message_loop.h',
+          'message_loop_helpers.h',
           'message_loop_proxy.cc',
           'message_loop_proxy.h',
           'message_loop_proxy_impl.cc',
@@ -252,6 +253,9 @@
           'scoped_native_library.h',
           'scoped_temp_dir.cc',
           'scoped_temp_dir.h',
+          'sequenced_task_runner.cc',
+          'sequenced_task_runner.h',
+          'sequenced_task_runner_helpers.h',
           'sha1.h',
           'sha1_portable.cc',
           'sha1_win.cc',
@@ -259,6 +263,7 @@
           'shared_memory_android.cc',
           'shared_memory_posix.cc',
           'shared_memory_win.cc',
+          'single_thread_task_runner.h',
           'spin_wait.h',
           'stack_container.h',
           'stl_util.h',
@@ -311,6 +316,8 @@
           'sys_string_conversions_mac.mm',
           'sys_string_conversions_posix.cc',
           'sys_string_conversions_win.cc',
+          'task_runner.cc',
+          'task_runner.h',
           'template_util.h',
           'threading/non_thread_safe.h',
           'threading/non_thread_safe_impl.cc',