base TaskTimeObserver: Record alloc stacks for investigation

TaskTimeObservers are being used-after-free. This investigates which
component is not unregistering observers correctly. It will be
reverted before beta, because unwinding the stack every
TaskTimeObserver creation occurs is a bad idea.

Bug: 337200890
Change-Id: I6bbcde1d4ae098122f5f388765d42b1a3a3ffc51
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5596490


Auto-Submit: Sean Maher <spvw@chromium.org>
Commit-Queue: Sean Maher <spvw@chromium.org>
Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1310109}