Add base/files/file_tracing.cc to tools/gn/bootstrap/bootstrap.py. BUG=491951 Review URL: https://codereview.chromium.org/1144003003 Cr-Original-Commit-Position: refs/heads/master@{#331315} Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src Cr-Mirrored-Commit: 58a1b336e86f925eac8054e6d73f12bc026bbe60