[vm/aot] Clean up old assumptions in Serializer::WriteInstructions().

In the past, negative text offsets were used for instructions shared
by multiple code objects. This is no longer the case.

Cq-Include-Trybots: luci.dart.try:vm-kernel-precomp-linux-release-x64-try,vm-kernel-precomp-linux-product-x64-try,vm-kernel-precomp-linux-debug-x64-try
Change-Id: I85085a06b8c955abb21573caea5554e839154979
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/149281
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Tess Strickland <sstrickl@google.com>

https://dart.googlesource.com/sdk/+/d881462eaeafbd62515d27a5a741aabe2726fafa
1 file changed
tree: dc1383c554253e557c4bd1fdd384f4efd0e22fd8
  1. commits.json