Reject empty protocol id in HTTP/2 ALTSVC frames.

net/spdy/spdy_framer.cc

Index: net/spdy/spdy_framer.cc
diff --git a/net/spdy/spdy_framer.cc b/net/spdy/spdy_framer.cc
index ea5eaa564b3b9b92667fd03bac10d1f59ce1a943..49a73a581eb54b9ba929e5c5fa76aaa990e6df29 100644
--- a/net/spdy/spdy_framer.cc
+++ b/net/spdy/spdy_framer.cc
@@ -2056,8 +2056,9 @@ size_t SpdyFramer::ProcessAltSvcFramePayload(const char* data, size_t len) {
                           reader.ReadUInt8(&altsvc_scratch_.pid_len);
         DCHECK(successful_read);
         // Sanity check length value.
-        if (GetAltSvcMinimumSize() + altsvc_scratch_.pid_len >=
-            current_frame_length_) {
+        if (altsvc_scratch_.pid_len == 0 ||
+            GetAltSvcMinimumSize() + altsvc_scratch_.pid_len >=
+                current_frame_length_) {
           set_error(SPDY_INVALID_CONTROL_FRAME);
           return 0;
         }