Bug 118163 [Dialogs] - PopupDialog should define constants for zero margins
PopupDialogs traditionally use a 0 margin width and height for the grid layouts used. This should be made an API constant rather than subclasses just knowing.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/PopupDialog.java
* Overriding <code>createDialogArea</code> and (optionally)
	 * <code>createTitleMenuArea</code> and <code>createTitleMenuArea</code>
	 * are recommended rather than overriding this method.
	 * 
	 * @param parent
	 *            the composite used to parent the contents.
	 * 
	 * @return the control representing the contents.
	 */
	protected Control createContents(Composite parent) {
		Composite composite = new Composite(parent, SWT.NONE);
		GridLayout layout = new GridLayout(1, false);
		layout.marginHeight = POPUP_MARGINHEIGHT;
		layout.marginWidth = POPUP_MARGINWIDTH;
		layout.verticalSpacing = POPUP_VERTICALSPACING;
		composite.setLayout(layout);
		GridData gd = new GridData(GridData.FILL_BOTH);
		composite.setLayoutData(gd);
		
		if (hasTitleArea()) {
			createTitleMenuArea(composite);
			titleSeparator = createHorizontalSeparator(composite);
		}
		
		dialogArea = createDialogArea(composite);
		
		if (hasInfoArea()) {
			infoSeparator = createHorizontalSeparator(composite);
			createInfoTextArea(composite);
		}