This solves an awkward dependency cycle, where CalculatedStyleValue
needs the definition of Percentage, but including that would also pull
in PercentageOr, which in turn needs CalculatedStyleValue.
Many places that previously included StyleValue.h no longer need to. :^)
This remained undetected for a long time as HeaderCheck is disabled by
default. This commit makes the following file compile again:
// file: compile_me.cpp
#include <LibWeb/CSS/GridTrackSize.h>
// That's it, this was enough to cause a compilation error.
