drawShadow method
Draws a shadow for a Path representing the given material elevation.
The transparentOccluder
argument should be true if the occluding object
is not opaque.
The arguments must not be null.
Implementation
void drawShadow(Path path, Color color, double elevation, bool transparentOccluder) {
assert(path != null); // path is checked on the engine side
assert(color != null);
assert(transparentOccluder != null);
_drawShadow(path, color.value, elevation, transparentOccluder);
}