Remove GetProfilerMemorySize from HeapProfiler API.
Remove HeapObjectsMap::FindUntrackedObjects

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I32a9a0676485c17c08c068a8ca501525b0d2670e
Reviewed-on: https://chromium-review.googlesource.com/590651Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46984}