[dart2wasm] Fix some missed conversions on `_TypedData` getters.
[dart2wasm] Fix some missed conversions on `_TypedData` getters.

Change-Id: Ib246388aa0b48dff2ebf4704633b7ffc79b1b40a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/250560
Commit-Queue: Joshua Litt <9f8daed1ab51574c9a48ffacb03e4a1adb4f880c@google.com>
Reviewed-by: Aske Simon Christensen <589eb3fd9a84f06d0ac46d3aa71dddcfb0814ccd@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk