mac: Create a static mapping of accelerators in the main menu.

ui/base/cocoa/cocoa_event_utils.h

Index: ui/base/cocoa/cocoa_event_utils.h
diff --git a/ui/base/cocoa/cocoa_event_utils.h b/ui/base/cocoa/cocoa_event_utils.h
index fda1448d39a418167fdbc1997afc8141feab7073..e53930b24652f0b76a82b5aa87685707026ac471 100644
--- a/ui/base/cocoa/cocoa_event_utils.h
+++ b/ui/base/cocoa/cocoa_event_utils.h
@@ -15,6 +15,9 @@ namespace ui {
 // Retrieves a bitsum of ui::EventFlags represented by |event|,
 UI_BASE_EXPORT int EventFlagsFromNSEvent(NSEvent* event);
 
+// Converts the Cocoa |modifiers| bitsum into a ui::EventFlags bitsum.
+UI_BASE_EXPORT int EventFlagsFromModifiers(NSUInteger modifiers);
+
 // Retrieves a bitsum of ui::EventFlags represented by |event|,
 // but instead use the modifier flags given by |modifiers|,
 // which is the same format as |-NSEvent modifierFlags|. This allows