CSS parser includes all media under "all"

[pjt33]

Consider the following CSS:

@media print {
    foo { bar: baz }
}

This should only affect media "print". However, it's being parsed by ParseStyleBlocks and inserted under media "all" before being parsed again by ParseMediaStyleBlocks and inserted under media "print".

Code which demonstrates this:

var testCSS = @"
@media print {
    foo { bar: baz }
}";
var css = CssData.Parse(adapter, testCSS, false);
Assert(css.GetCssBlock("foo", "print").First().Properties["bar"] == "baz");
Assert(!css.GetCssBlock("foo", "all").Any(block => block.Properties.ContainsKey("bar")));

This bug then has knock-on effects because the default CSS includes an @media print section with h1 { page-break-before: always }, which is thoroughly undesirable in the WPF renderer.