GitLab

- Adds a directory under tools/perf/core where all the tbmv3 code will be
landed as we're experimenting with them.
- Adds a very basic run_tbmv3_metric script. Currently it consumes the output
  of trace processor and prints it back to the terminal. In subsequent CLs we
  will turn this output into a python histogram and output that instead.
- Adds console_error_metric as an example tbmv3 metric. You can run it using
    ./run_tbmv3_metric.py --trace TRACE_FILE --metric console_error_metric

Bug: chromium:1012687

Change-Id: I668268e707ae633b271256125e8a6d78701906f5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1846065
Commit-Queue: Deepanjan Roy <dproy@chromium.org>
Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705566}