[libfuzzer] add new source code file FuzzerTracePC.cpp into BUILD.gn.
[libfuzzer] add new source code file FuzzerTracePC.cpp into BUILD.gn.

R=aizatsky@chromium.org, inferno@chromium.org, kcc@chromium.org
BUG=539572
TBR=aizatsky@chromium.org

Review URL: https://codereview.chromium.org/1745093002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#378221}

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