MacViews: Implement Window-modal dialogs using sheets

ui/views/cocoa/views_nswindow_delegate.h

Index: ui/views/cocoa/views_nswindow_delegate.h
diff --git a/ui/views/cocoa/views_nswindow_delegate.h b/ui/views/cocoa/views_nswindow_delegate.h
index d5ef872ee078e3c41aeb77a627391a2ac44d84c8..ec8e6e1378d33c432990b692646094314d6c4cd3 100644
--- a/ui/views/cocoa/views_nswindow_delegate.h
+++ b/ui/views/cocoa/views_nswindow_delegate.h
@@ -47,6 +47,11 @@ class BridgedNativeWidget;
 // Notify when -[NSWindow display] is being called on the window.
 - (void)onWindowWillDisplay;
 
+// Called on the delegate of a modal sheet when its modal session ends.
+- (void)sheetDidEnd:(NSWindow*)sheet
+         returnCode:(NSInteger)returnCode
+        contextInfo:(void*)contextInfo;
+
 @end
 
 #endif  // UI_VIEWS_COCOA_VIEWS_NSWINDOW_DELEGATE_H_