Because of our port of css animation and css transition to
progress tracker, we should not think of animated styles as
immutable objects that can map any timestamp to css values.
Rather, timestamps can correspond to different values depending
on the value of GTK_SLOWDOWN over the course of the animation.
To keep animated styles and style animations totally immutable,
we will not share styleanimations between animatedstyles, and
make a new copy of a styleanimation for each timestamp.
Instead of keeping an animated style everywhere, we replace it with the
static style when nothing gets animated.
Apart from making the code cleaner, this gets rid of a bunch of animated
style values that do nothing but wrap a static style.
For now, this is only an implementation detail of the animated style.
The idea is to use GtkCssStaticStyle as the result of CSS queries and
then put a GtkCssAnimatedStyle on top that manages the animations. The
neat thing about this is that you can cache the static values.
GtkCssStyle is the base class to be used for all types of styles that do
exist.
GtkCssAnimatedStyle is the only implementation so far, that is exactly a
copy/paste of the old GtkCssStyle code.
