tracing: remove UNSHIPPED_TRACE_EVENT

Curently there is only one use case for UNSHIPPED_TRACE_EVENT* in the
codebase and that doesn't justify adding another dimension to the
combinatorial bloat of the tracing macros.
Just moving the OFFICIAL_BUILD check to the only use case.

BUG=

Review-Url: https://codereview.chromium.org/2397373003
Cr-Commit-Position: refs/heads/master@{#423904}
2 files changed