Statistical stack profiler for Windows x64

Provides the collection part of a client stack collection pipeline for
Win x64. This is intended to be used initially to provide real-world
stack trace data to UMA to facilitate implementation of server-side
processing. This CL has just the profiler implementation. Instantiation
and use of the profiler in Chrome, and handling by UMA, will be
addressed in follow-on CLs.

BUG=464929

Review URL: https://codereview.chromium.org/1016563004

Cr-Commit-Position: refs/heads/master@{#321658}
8 files changed