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 923a43dcd0fd2ea8f34d40529f6f5f5aeb5c7995..2bbca9175974b3cd6d4c6bbaabd7bcc97d0e1bf7 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -95,6 +95,9 @@
           'eintr_wrapper.h',
           'environment.cc',
           'environment.h',
+          'executor.cc',
+          'executor.h',
+          'executor_helpers.h',
           'file_descriptor_posix.h',
           'file_path.cc',
           'file_path.h',
@@ -186,6 +189,7 @@
           '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',
@@ -251,6 +255,7 @@
           'scoped_native_library.h',
           'scoped_temp_dir.cc',
           'scoped_temp_dir.h',
+          'serial_executor.h',
           'sha1.h',
           'sha1_portable.cc',
           'sha1_win.cc',
@@ -258,6 +263,7 @@
           'shared_memory_android.cc',
           'shared_memory_posix.cc',
           'shared_memory_win.cc',
+          'single_thread_executor.h',
           'spin_wait.h',
           'stack_container.h',
           'stl_util.h',