Add greping for values to tracetool
Add greping for values to tracetool

Adds the ability to grep for a specific string in the
values of a commit range. This only makes sense for
gold data since perf stores serialized floats.

BUG=skia:
R=jcgregorio

Review-Url: https://codereview.chromium.org/1955863003

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot