Currently RuntimeCallStats stores CounterIds as inner pointers.
This patch replaces them with enums and removes static table.

Bug: chromium:758183
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Icb4030fc3ad3dd02e9c2648ce7c43b6f2d47fa9d
Reviewed-on: https://chromium-review.googlesource.com/796477Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49743}