Bug 202316 [Forms] Add gradient sharing support for FormHeading
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/internal/forms/widgets/FormHeading.java
return JFaceResources.getImage(Dialog.DLG_IMG_MESSAGE_WARNING);
			case IMessageProvider.ERROR:
				return JFaceResources.getImage(Dialog.DLG_IMG_MESSAGE_ERROR);
			default:
				return null;
			}
		}
		public void addMessageHyperlinkListener(IHyperlinkListener listener) {
			if (listeners == null)
				listeners = new ListenerList();
			listeners.add(listener);
			ensureControlExists();
			if (messageHyperlink != null)
				messageHyperlink.addHyperlinkListener(listener);
			if (listeners.size() == 1)
				updateForeground();
		}
		private void removeMessageHyperlinkListener(IHyperlinkListener listener) {
			if (listeners != null) {
				listeners.remove(listener);
				if (messageHyperlink != null)
					messageHyperlink.removeHyperlinkListener(listener);
				if (listeners.isEmpty())
					listeners = null;
				ensureControlExists();
				if (listeners == null && !isDisposed())
					updateForeground();
			}
		}
		private void ensureControlExists() {