Separated out of CL:1513058 to make it possible to land parts
individually while the affected crate has no other significant CLs
pending. This avoids repeatedly introducing non-textual conflicts with
new code that adds `use` statements.
TEST=cargo check
TEST=cargo check --all-features
TEST=cargo check --target aarch64-unknown-linux-gnu
Change-Id: I4f6c91c966afc96fad634e355553ab90fc305261
Reviewed-on: https://chromium-review.googlesource.com/1519698
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: David Tolnay <dtolnay@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: David Tolnay <dtolnay@chromium.org>