tree 3225c9271dd55535856c098d3d612e5c3dc907d2
parent 458129d12c6d8b70e4e00fc3afa217e3915ba14c
author Googler <noreply@google.com> 1613138606 -0800
committer Nate Bosch <nbosch1@gmail.com> 1613601192 -0800

Migrating to `dart:ffi` in Dart 2.12 and `package:ffi` 1.0.0.

Migrates:
- `allocate` and `free` to `calloc` and `calloc.free`.
- `Utf8.toUtf8`, `Utf8.fromUtf8`, `Utf16.toUtf16` and , `Utf16.fromUtf16` to new
  extension methods `toNativeUtf8`, `toNativeUtf16`, and `toDartString`.
- empty `Struct`s to `Opaque`.

Tested:
    TAP for global presubmit queue
    http://test/OCL:357169869:BASE:357174266:1613138261627:d1691ac7
PiperOrigin-RevId: 357175000