Revert of win: Fix current toolchain path with old packaging (patchset #1 id:1 of https://codereview.chromium.org/1159433006/)

Reason for revert:
Breaking chromium waterfall.

Original issue's description:
> win: Fix current toolchain path with old packaging
> 
> I broke boringssl's use of depot_tools toolchain as I changed the
> name of the sdk path key. This happened to work in Chrome because
> src/ has fallback behaviour.
> 
> Restore the 'win8sdk' name when unpacking a current/old-style
> toolchain package (i.e. what everyone is still using).
> 
> TBR=dpranke@chromium.org
> R=davidben@chromium.org
> 
> Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=295492

TBR=davidben@chromium.org,dpranke@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/1167753003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295493 0039d316-1c4b-4281-b951-d872f2087c98