We only had the tracing on didChange before this
Change-Id: Iadec8a43d439931bf58925f149a1d32b3ae29c36
Reviewed-on: https://go-review.googlesource.com/c/tools/+/186199
Run-TryBot: Ian Cottrell <iancottrell@google.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>