fillRange method
Sets the objects in the range start inclusive to end exclusive
to the given fillValue.
The provided range, given by start and end, must be valid.
A range from start to end is valid if 0 <= start <= end <= len, where
len is this list's length. The range starts at start and has length
end - start. An empty range (with end == start) is valid.
Example:
List<int> list = new List(3);
list.fillRange(0, 2, 1);
print(list); // [1, 1, null]
Implementation
void fillRange(int start, int end, [E fillValue]);