Fixed the racy code around the message-only window in base::MessagePumpForUI on Windows.

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index abfe1f5ef86196e589d4b4eac115f1a41e33ef49..8284f43caa565ffad7564344d91dbb75687430ea 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -553,8 +553,8 @@
           'nix/mime_util_xdg.h',
           'nix/xdg_util.cc',
           'nix/xdg_util.h',
-          'win/enum_variant.h',
           'win/enum_variant.cc',
+          'win/enum_variant.h',
           'win/event_trace_consumer.h',
           'win/event_trace_controller.cc',
           'win/event_trace_controller.h',
@@ -564,8 +564,10 @@
           'win/i18n.h',
           'win/iat_patch_function.cc',
           'win/iat_patch_function.h',
-          'win/iunknown_impl.h',
           'win/iunknown_impl.cc',
+          'win/iunknown_impl.h',
+          'win/message_window.cc',
+          'win/message_window.h',
           'win/metro.cc',
           'win/metro.h',
           'win/object_watcher.cc',
@@ -598,10 +600,10 @@
           'win/startup_information.h',
           'win/text_services_message_filter.cc',
           'win/text_services_message_filter.h',
-          'win/windows_version.cc',
-          'win/windows_version.h',
           'win/win_util.cc',
           'win/win_util.h',
+          'win/windows_version.cc',
+          'win/windows_version.h',
           'win/wrapped_window_proc.cc',
           'win/wrapped_window_proc.h',
         ],