The line number is associated with each sample along with pointer
to the ProfileNode and timeDelta. Once collected line numbers are
streamed as an array of integers in "ProfileChunk" trace events.

If all the line numbers are zero, the array may be omitted. Otherwise
the array length matches length of samples and timeDeltas arrays.

BUG=chromium:925089

Change-Id: I1ef5cd1b208b03bb127f4d17b1efa74c01959542
Reviewed-on: https://chromium-review.googlesource.com/c/1459739Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59514}