Using CpuProfile pointer is not safe for id as the profile objects
can be recreated on the same memory address.
Use sequential numbers instead.

Change-Id: I7253605819055bc3396b797f9ce27669e8c2584d
Reviewed-on: https://chromium-review.googlesource.com/1123325Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54180}