Bug 26109 [Dialogs] Need a FormData version of the button sizing API
The button sizing API in Dialog assumes the developer wants a GridData. We should promote the FormData version in PathVariablesDialog to Dialog.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/Dialog.java
layout.numColumns = 0; 
	layout.makeColumnsEqualWidth = true;
	layout.marginWidth = convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_MARGIN);
	layout.marginHeight = convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_MARGIN);
	layout.horizontalSpacing = convertHorizontalDLUsToPixels(IDialogConstants.HORIZONTAL_SPACING);
	layout.verticalSpacing = convertVerticalDLUsToPixels(IDialogConstants.VERTICAL_SPACING);
	composite.setLayout(layout);
	GridData data = new GridData(
		GridData.HORIZONTAL_ALIGN_END |
		GridData.VERTICAL_ALIGN_CENTER);
	composite.setLayoutData(data);
	composite.setFont(parent.getFont());
	
	
	createButtonsForButtonBar(composite);
	return composite;
}
/**
 * Adds buttons to this dialog's button bar.
 * <p>
 * The <code>Dialog</code> implementation of this framework method adds 
 * standard ok and cancel buttons using the <code>createButton</code>
 * framework method. These standard buttons will be accessible from 
 * <code>getCancelButton</code>, and <code>getOKButton</code>.
 * Subclasses may override.
 * </p>
 *
 * @param parent the button bar composite
 */
protected void createButtonsForButtonBar(Composite parent) {