[Mac] Move UI item validation to UserInterfaceItemCommandHandler.

ui/views/cocoa/native_widget_mac_nswindow.mm

Index: ui/views/cocoa/native_widget_mac_nswindow.mm
diff --git a/ui/views/cocoa/native_widget_mac_nswindow.mm b/ui/views/cocoa/native_widget_mac_nswindow.mm
index 1de283fb956b7dc53d180ed36ec06e1e07d4ae91..c3c30801410f16c9c276dd78edc5f727cb4c5c8e 100644
--- a/ui/views/cocoa/native_widget_mac_nswindow.mm
+++ b/ui/views/cocoa/native_widget_mac_nswindow.mm
@@ -23,6 +23,7 @@
 @implementation NativeWidgetMacNSWindow {
  @private
   base::scoped_nsobject<CommandDispatcher> commandDispatcher_;
+  id<UserInterfaceItemCommandHandler> commandHandler_;
 }
 
 - (instancetype)initWithContentRect:(NSRect)contentRect
@@ -40,8 +41,10 @@
 
 // Public methods.
 
-- (void)setCommandDispatcherDelegate:(id<CommandDispatcherDelegate>)delegate {
+- (void)setCommandDispatcherDelegate:
+    (id<CommandDispatcherDelegate, UserInterfaceItemCommandHandler>)delegate {
   [commandDispatcher_ setDelegate:delegate];
+  commandHandler_ = delegate;
 }
 
 // Private methods.
@@ -168,4 +171,19 @@
   return [super performKeyEquivalent:event];
 }
 
+- (void)commandDispatch:(id)sender {
+  [commandHandler_ commandDispatch:sender window:self];
+}
+
+- (void)commandDispatchUsingKeyModifiers:(id)sender {
+  [commandHandler_ commandDispatchUsingKeyModifiers:sender window:self];
+}
+
+// NSWindow overrides (NSUserInterfaceItemValidations implementation)
+
+- (BOOL)validateUserInterfaceItem:(id<NSValidatedUserInterfaceItem>)item {
+  return [commandHandler_ validateUserInterfaceItem:item window:self] &&
+         [super validateUserInterfaceItem:item];
+}
+
 @end