Avoid SpdyHeaderBlock copy in SpdyStream::OnPushPromiseHeadersReceived().

net/spdy/header_coalescer.cc

Index: net/spdy/header_coalescer.cc
diff --git a/net/spdy/header_coalescer.cc b/net/spdy/header_coalescer.cc
index eb8d3816503f7fb68b262db36130370db79b07c1..1c88fbab6a36a778c4b46e9ae115a583a8849aee 100644
--- a/net/spdy/header_coalescer.cc
+++ b/net/spdy/header_coalescer.cc
@@ -4,6 +4,8 @@
 
 #include "net/spdy/header_coalescer.h"
 
+#include <utility>
+
 #include "base/strings/string_util.h"
 
 namespace net {
@@ -55,4 +57,10 @@ void HeaderCoalescer::OnHeader(base::StringPiece key, base::StringPiece value) {
   }
 }
 
+SpdyHeaderBlock HeaderCoalescer::release_headers() {
+  DCHECK(headers_valid_);
+  headers_valid_ = false;
+  return std::move(headers_);
+}
+
 }  // namespace net