[tools/perf] Add link to mock benchmark documentation in dummy_becnhmark.py description
[tools/perf] Add link to mock benchmark documentation in dummy_becnhmark.py description

BUG=537676

Review URL: https://codereview.chromium.org/1445443002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#359636}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk