ui/base: Move message_box_win.{h,cc} to ui/base/win.

ui/base/ui_base_switches.cc

Index: ui/base/ui_base_switches.cc
diff --git a/ui/base/ui_base_switches.cc b/ui/base/ui_base_switches.cc
index 8f805fed2eda152563004353e9f574f031a5641e..df2d44b7bb9fc0d685b13c784ad2d0c033f8c025 100644
--- a/ui/base/ui_base_switches.cc
+++ b/ui/base/ui_base_switches.cc
@@ -17,6 +17,10 @@ const char kLocalePak[]                     = "locale_pak";
 // Enables UI changes that make it easier to use with a touchscreen.
 const char kTouchOptimizedUI[]              = "touch-optimized-ui";
 
+// Disable ui::MessageBox.  This is useful when running as part of scripts that
+// do not have a user interface.
+const char kNoMessageBox[]                  = "no-message-box";
+
 #if defined(OS_MACOSX)
 const char kDisableCompositedCoreAnimationPlugins[] =
     "disable-composited-core-animation-plugins";