Restricts linux perf-event code range reporting to functions only (i.e. on
stubs.) While this makes the gathered ticks less accurate, it reduces the
growth of the /tmp/perf-${pid}.map file.

BUG=v8:3453
R=hablich@chromium.org,danno@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/1292743002

Cr-Commit-Position: refs/heads/master@{#30179}