wrapAll method
Wraps each of the given children in RepaintBoundarys.
The key for each RepaintBoundary is derived either from the wrapped child's key (if the wrapped child has a non-null key) or from the wrapped child's index in the list.
Implementation
static List<RepaintBoundary> wrapAll(List<Widget> widgets) {
final List<RepaintBoundary> result = List<RepaintBoundary>(widgets.length);
for (int i = 0; i < result.length; ++i)
result[i] = RepaintBoundary.wrap(widgets[i], i);
return result;
}