The versions of dbghelp.dll that ship with the latest 10.0.14393.0 SDK
(yes, there are multiple versions) as of the VS 2017 launch cannot
handle /debug:fastlink binaries created by VS 2017. This leads to hangs
during symbol lookup, as reported here:
https://developercommunity.visualstudio.com/content/problem/36255/chromes-base-unittests-fails-with-vs-2017-due-to-s.html
The recommended fix is to copy dbghelp.dll from the VS install instead,
from Common7\IDE\CommonExtensions\Microsoft\TestWindow\Extensions\CppUnitFramework

Without this fix base_unittests will hang and windbg will not work on
/debug:fastlink binaries. With this fix base_unittests completes
promptly.

BUG=683729

Change-Id: Ie58b9d898a1feb04f11e99891035d2e40a2a9c0f
Reviewed-on: https://chromium-review.googlesource.com/461385Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>