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..a5210537ab407cfd7ab00e9bbb25f71e530d3625 100644
--- a/ui/base/ui_base_switches.cc
+++ b/ui/base/ui_base_switches.cc
@@ -6,7 +6,7 @@
 
 namespace switches {
 
-// The language file that we want to try to open.  Of the form
+// The language file that we want to try to open. Of the form
 // language[-country] where language is the 2 letter code from ISO-639.
 const char kLang[]                          = "lang";
 
@@ -14,6 +14,10 @@ const char kLang[]                          = "lang";
 // path should point to a locale.pak file.
 const char kLocalePak[]                     = "locale_pak";
 
+// 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";
+
 // Enables UI changes that make it easier to use with a touchscreen.
 const char kTouchOptimizedUI[]              = "touch-optimized-ui";