Add error reporting mechanism for failing Unwind.

Remove the logging of an error if a thread disappears before the unwind
can begin. This can happen, so allow the caller to determine if this
is really a problem worth logging.

Bug: 27449879
Change-Id: Ie81718d53fb0e519fa0a7db9fd5f314b72bfa431
6 files changed
tree: 587b9328b9195b7366aeaf20e9ed8eac8835a17c
  1. libbacktrace/