dispose method
Release the resources used by this object. The object is no longer usable after this method is called.
The underlying memory allocated by this object will be retained beyond this call if it is still needed by another object that has not been disposed. For example, a Picture that has not been disposed that refers to an ImageShader may keep its underlying resources alive.
Classes that override this method must call super.dispose()
.
Implementation
void dispose() {
assert(() {
assert(!_debugDisposed);
_debugDisposed = true;
return true;
}());
}