Also add a SignedBitField alias so that sign extended BitFields can
be declared with default positions and/or sizes.
TEST=ci
Change-Id: I46bf7f9e378e0f20e7f2e4b4e7ed3e242946d9bb
Cq-Include-Trybots: luci.dart.try:vm-aot-dwarf-linux-product-x64-try,vm-aot-linux-debug-x64c-try,vm-aot-linux-release-x64-try,vm-aot-mac-release-arm64-try,vm-aot-linux-release-simarm_x64-try,vm-win-release-arm64-try,vm-aot-win-release-arm64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/382404
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Tess Strickland
27e15ae053