Sets the objects in the range start inclusive to end exclusive
to the given fillValue.
The provide 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.
Source
void fillRange(int start, int end, [E fillValue]) {
throw new UnsupportedError("Cannot modify an immutable List.");
}