[tracing] Add test for memory-infra startup tracing
This is a follow-up to crrev.com/1333873002 that introduced
support to startup tracing.
Also this change refactors the TraceConfig JSON used by
various memory-infra tests (in and out of base) into a
test_util.h file.
Furthermore this change fixes a off-by-one mistake in the
periodic scheduler (and its test).
BUG=524057
Review URL: https://codereview.chromium.org/1335503003
Cr-Commit-Position: refs/heads/master@{#348373}
CrOS-Libchrome-Original-Commit: 26b6f415865b7eab46b099d5773fbc0cb9e98b77
7 files changed