Support black background color schemes for Chromium in debugging mode (was part of #15)

[paulvi]

This is continuation of #15 , which was partly closed.

[paulvi]

This actually not solved. Some words are still black on black.
@gurok Are you using 0.6 ?

[paulvi]

jeeeyul/eclipse-themes#106 suggests

IThemeEngine engine = (IThemeEngine) Display.getDefault().getData("org.eclipse.e4.ui.css.swt.theme");