[Sampling profiler] Use self-reported function start address in unwind tests

For functions to be unwound, requests the address near the start of the
function from the function itself rather than using the function pointer
value. This enables the use of functions on the stack to be unwound for
which we can't easily obtain a function pointer (e.g. Callbacks) and
eliminates the need to special case incremental linking.

Bug: 909957
Change-Id: Ib08fac1bf3cca12a607af6c3a0ffd939924de443
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574291
Commit-Queue: Mike Wittman <wittman@chromium.org>
Reviewed-by: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653166}
1 file changed