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/1118222Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Commit-Queue: Oscar Johansson <oscarj@opera.com>
Cr-Commit-Position: refs/heads/master@{#571450}

net/third_party/quic/core/crypto/crypto_utils.cc

@@ -457,4 +457,5 @@ void CryptoUtils::HashHandshakeMessage(const CryptoHandshakeMessage& message,
   output->assign(reinterpret_cast<const char*>(digest), sizeof(digest));
 }
 
+#undef RETURN_STRING_LITERAL  // undef for jumbo builds
 }  // namespace quic

net/third_party/quic/core/quic_error_codes.cc

@@ -162,4 +162,5 @@ void RecordInternalErrorLocation(QuicInternalErrorLocation location) {
                             INTERNAL_ERROR_LOCATION_MAX);
 }
 
+#undef RETURN_STRING_LITERAL  // undef for jumbo builds
 }  // namespace quic

net/third_party/quic/core/quic_utils.cc

@@ -321,4 +321,5 @@ bool QuicUtils::IsIetfPacketHeader(uint8_t first_byte) {
          !(first_byte & FLAGS_DEMULTIPLEXING_BIT);
 }
 
+#undef RETURN_STRING_LITERAL  // undef for jumbo builds
 }  // namespace quic

net/third_party/quic/core/quic_versions.cc

@@ -325,4 +325,5 @@ QuicString ParsedQuicVersionVectorToString(
   return result;
 }
 
+#undef RETURN_STRING_LITERAL  // undef for jumbo builds
 }  // namespace quic