Reset the trace_marker pointer after deletion

BUG=chromium-os:34099
TEST=unittest

Change-Id: If1ca0b2bf6dd8fc4456f127ec0ea7f74d3617334
Reviewed-on: https://gerrit.chromium.org/gerrit/32101
Reviewed-by: Andrew de los Reyes <adlr@chromium.org>
Commit-Ready: Chung-yih Wang <cywang@chromium.org>
Reviewed-by: Chung-yih Wang <cywang@chromium.org>
Tested-by: Chung-yih Wang <cywang@chromium.org>
3 files changed