ProcessReader is responsible for collecting information needed to build
a snapshot of the target process, independent of the Snapshot
interface. This CL includes implementation and tests for collecting
thread information, but does not yet collect module information.
Bug: crashpad:30
Change-Id: I911f155c953129a5fa8c031e923c0de2bd740ce0
Reviewed-on: https://chromium-review.googlesource.com/488162
Reviewed-by: Mark Mentovai <mark@chromium.org>
