libweave: Fixed _DEBUG build

One DPCHECK was not previously removed.
Added BASE_EXPORT used by FROM_HERE.

BUG=none
TEST=none

Change-Id: Icce0fb6d46f9961f70e74f9465e22bebbbdd0fe9
Reviewed-on: https://chromium-review.googlesource.com/295216
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>