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
* width of the given number of characters.
 * <p>
 * This method may only be called after <code>initializeDialogUnits</code>
 * has been called.
 * </p>
 * <p>
 * Clients may call this framework method, but should not override it.
 * </p>
 *
 * @param chars the number of characters
 * @return the number of pixels
 */
protected int convertWidthInCharsToPixels(int chars) {
	
	if (fontMetrics == null)
		return 0;
	return convertWidthInCharsToPixels(fontMetrics, chars);
}
/**
 * Creates a new button with the given id.
 * <p>
 * The <code>Dialog</code> implementation of this framework method
 * creates a standard push button, registers it for selection events
 * including button presses, and registers default buttons with its shell.
 * The button id is stored as the button's client data.  If the button id 
 * is <code>IDialogConstants.CANCEL_ID</code>, the new button will be 
 * accessible from <code>getCancelButton()</code>.  If the button id is 
 * <code>IDialogConstants.OK_ID</code>, the new button will be accesible 
 * from <code>getOKButton()</code>.  Note that the parent's layout 
 * is assumed to be a <code>GridLayout</code> and the number of columns in this