84a66d82d3added support for light and dark themes, but dark themes weren't enabled, as diff styles have to be adjusted to correspond with dark colors.101a8c4b65reverted the preparation for dark themes support. This change enables support for subset of dark themes and switch dynamicaly the diff styles to dark colors, when dark theme was selected. Change-Id: Ic220baf8f19366c04520b61e893a0d11912805ef