css-logical/animation-004.html is a bit buggy

[Loirooriol]

https://github.com/web-platform-tests/wpt/blob/master/css/css-logical/animation-004.html is supposed to accept start and end values for various properties, and then test that the computed value is half-way, because the property can be transitioned.

The problem is that the start values are added at the same time as the transition properties (and not before), so in fact the transition starts from the initial value. If the test works it's because most start values are 0.

But for example,

test(t => {
  transition(t, {
    "margin-inline-start": "100px",
  }, {
    "margin-left": "200px",
  });
  assert_equals(getComputedStyle(testEl).marginLeft, '150px');
});

will get 125px instead of 150px, a bit unexpected.