Creates a Int64List view of a region of this byte buffer.
The view is backed by the bytes of this byte buffer.
Any changes made to the Int64List will also change the buffer,
and vice versa.
The viewed region start at offsetInBytes, which must be 64-bit aligned,
and contains length 64-bit integers.
If length is omitted, the range extends as far towards the end of
the buffer as possible -
if lengthInBytes is not divisible by eight, the last bytes can't be part
of the view.
The start index and length must describe a valid 64-bit aligned range of the buffer:
offsetInBytes must not be negative,offsetInBytes must be divisible by eight,length must not be negative, andoffsetInBytes + length * 8 must not be greater than lengthInBytes.Int64List asInt64List([int offsetInBytes = 0, int length]) =>
new UnmodifiableInt64ListView(_data.asInt64List(offsetInBytes, length));