Bug 295981 [Forms] FormImages & FormFonts are not disposed correctly
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/internal/forms/widgets/FormImages.java
public Image getGradient(Color color1, Color color2,
			int realtheight, int theight, int marginHeight) {
		if (color1 == null || color1.isDisposed() || color2 == null || color2.isDisposed())
			return null;
		AbstractImageDescriptor desc = new SimpleImageDescriptor(color1, color2, realtheight, theight, marginHeight);
		return getGradient(desc);
	}
	
	public Image getGradient(Color[] colors, int[] percents,
			int length, boolean vertical, Color bg) {
		if (colors.length == 0)
			return null;
		for (int i = 0; i < colors.length; i++)
			if (colors[i] == null || colors[i].isDisposed())
				return null;
		if (bg != null && bg.isDisposed())
			return null;
		AbstractImageDescriptor desc = new ComplexImageDescriptor(colors, length, percents, vertical, bg);
		return getGradient(desc);
	}
	
	private synchronized Image getGradient(AbstractImageDescriptor desc) {
		checkHashMaps();
		Image result = getResourceManager().createImage(desc);
		descriptors.put(result, desc);
		return result;
	}
	
	public synchronized boolean markFinished(Image image) {
		checkHashMaps();