Resolve RETURN_STRING_LITERAL macro conflict (net)

The macro RETURN_STRING_LITERAL is defined in namespaces in:
net/third_party/quic/core/crypto/crypto_utils.cc
net/third_party/quic/core/quic_error_codes.cc
net/third_party/quic/core/quic_utils.cc
net/third_party/quic/core/quic_versions.cc

When building using jumbo these end up in the same
namspace and conflict. This commit solves the issue
by undefining the macro inside the namespace.

Bug: 772146
Change-Id: Ibb07acd829f8ad2867748d1db8aba5aa59a39e47
Reviewed-on: https://chromium-review.googlesource.com/1118222
Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Commit-Queue: Oscar Johansson <oscarj@opera.com>
Cr-Commit-Position: refs/heads/master@{#571450}
4 files changed