Avoids the "re-encode HPACK as SPDY3" step.

net/quic/spdy_utils.cc

Index: net/quic/spdy_utils.cc
diff --git a/net/quic/spdy_utils.cc b/net/quic/spdy_utils.cc
index 90e65373827dc08b0052c52e8e019117d7f82813..bf50d7d29e1bf45cab6306084a8d4a22255d1fe0 100644
--- a/net/quic/spdy_utils.cc
+++ b/net/quic/spdy_utils.cc
@@ -120,12 +120,6 @@ bool SpdyUtils::CopyAndValidateHeaders(const QuicHeaderList& header_list,
       return false;
     }
 
-    if (std::any_of(name.begin(), name.end(), base::IsAsciiUpper<char>)) {
-      DLOG(ERROR) << "Malformed header: Header name " << name
-                  << " contains upper-case characters.";
-      return false;
-    }
-
     auto iter = headers->find(name);
     if (iter == headers->end()) {
       (*headers)[name] = p.second;