We need two repos to get jsoncpp working. First is the Chromium tree
mirror and second is the jsoncpp source itself. The Chromium version
includes only the build files and some source file overrides.

Bug: angleproject:2794
Change-Id: I0e1acaf783c5ae3935803eacdf93ffbe01f9fe4d
Reviewed-on: https://chromium-review.googlesource.com/1210562Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Commit-Queue: Jamie Madill <jmadill@chromium.org>