[Mac] Move UI item validation to UserInterfaceItemCommandHandler.

ui/base/cocoa/command_dispatcher.h

Index: ui/base/cocoa/command_dispatcher.h
diff --git a/ui/base/cocoa/command_dispatcher.h b/ui/base/cocoa/command_dispatcher.h
index 8ad679af00ed3df90039e57332e870e8f88714ac..8e387323b0ee5f07d7424edbab4739725c69273c 100644
--- a/ui/base/cocoa/command_dispatcher.h
+++ b/ui/base/cocoa/command_dispatcher.h
@@ -12,6 +12,7 @@
 
 @protocol CommandDispatcherDelegate;
 @protocol CommandDispatchingWindow;
+@protocol UserInterfaceItemCommandHandler;
 
 // CommandDispatcher guides the processing of key events to ensure key commands
 // are executed in the appropriate order. In particular, it allows a first
@@ -89,6 +90,39 @@ UI_BASE_EXPORT @interface CommandDispatcher : NSObject
 // CommandDispatcher calls as part of its -performKeyEquivalent: flow.
 - (BOOL)defaultPerformKeyEquivalent:(NSEvent*)event;
 
+// AppKit will call -[NSUserInterfaceValidations validateUserInterfaceItem:] to
+// validate UI items. Any item whose target is FirstResponder, or nil, will
+// traverse the responder chain looking for a responder that implements the
+// item's selector. Thus NSWindow is usually the last to be checked and will
+// handle any items that are not validated elsewhere in the chain. Implement the
+// following so that menu items with these selectors are validated by
+// CommandDispatchingWindow.
+- (void)commandDispatch:(id)sender;
+- (void)commandDispatchUsingKeyModifiers:(id)sender;
+
+@end
+
+// Used by CommandDispatchingWindow to implement UI item validation.
+@protocol UserInterfaceItemCommandHandler
+
+// Called by CommandDispatchingWindow to validate menu and toolbar items. All
+// the items we care about have been set with the -commandDispatch or
+// -commandDispatchUsingKeyModifiers selectors and a target of FirstResponder in
+// IB. If it's not one of those, it should be handled elsewhere in the responder
+// chain.
+- (BOOL)validateUserInterfaceItem:(id<NSValidatedUserInterfaceItem>)item
+                           window:(NSWindow*)window;
+
+// Called by CommandDispatchingWindow to execute commands. This assumes that the
+// command is supported and doesn't check, otherwise it would have been disabled
+// in the UI in validateUserInterfaceItem:.
+- (void)commandDispatch:(id)sender window:(NSWindow*)window;
+
+// Same as |-commandDispatch:|, but executes commands using a disposition
+// determined by the key flags. If the window is in the background and the
+// command key is down, ignore the command key, but process any other modifiers.
+- (void)commandDispatchUsingKeyModifiers:(id)sender window:(NSWindow*)window;
+
 @end
 
 #endif  // UI_BASE_COCOA_COMMAND_DISPATCHER_H_