Bug 273330 [JFace] Add API to MessageDialog to enable clients to use SWT.SHEET
A new style constant SWT.SHEET was added recently. Without adding new API in JFace, clients who are currently using the convenience methods MessageDialog.openWarning/Error/Information/Question/Confirmation would not be able to open these dialogs as sheets.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/MessageDialogWithToggle.java
return IDialogConstants.ABORT_ID;
		}
	    
	    if (IDialogConstants.RETRY_LABEL.equals(buttonLabel)) {
			return IDialogConstants.RETRY_ID;
		}
	    
	    if (IDialogConstants.IGNORE_LABEL.equals(buttonLabel)) {
			return IDialogConstants.IGNORE_ID;
		}
	    
	    if (IDialogConstants.PROCEED_LABEL.equals(buttonLabel)) {
			return IDialogConstants.PROCEED_ID;
		}
	    
	    if (IDialogConstants.OPEN_LABEL.equals(buttonLabel)) {
			return IDialogConstants.OPEN_ID;
		}
	    
	    if (IDialogConstants.CLOSE_LABEL.equals(buttonLabel)) {
			return IDialogConstants.CLOSE_ID;
		}
	    
	    if (IDialogConstants.BACK_LABEL.equals(buttonLabel)) {
			return IDialogConstants.BACK_ID;
		}
	    
	    if (IDialogConstants.NEXT_LABEL.equals(buttonLabel)) {
			return IDialogConstants.NEXT_ID;
		}