Add chromium's overrides.

Pulled from https://chromium.googlesource.com/chromium/src/third_party/jsoncpp.git@41239939c0c60481f34887d52c038facf05f5533
Smashed into chromium/overrides to keep it in the same project.

BUG:15087860

Change-Id: I0e461c2a6db73d78f5414df65a7436bb5b3dd4d4
3 files changed