libchromeos: Don't rely on the internal of std::string.

We should not rely on the fact that string copy might be done lazily.

BUG=None
TEST=`FEATURES=test emerge-gizmo libchromeos --nodeps` works.

Change-Id: Ie0a798b9be6347a715203b291d083757f8d66510
Reviewed-on: https://chromium-review.googlesource.com/287503
Trybot-Ready: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
1 file changed