Hit some esoteric request header paths

src/core/channel/http_server_filter.c

@@ -124,7 +124,6 @@ static grpc_mdelem *server_filter(void *user_data, grpc_mdelem *md) {
        omitted */
     grpc_mdelem *authority = grpc_mdelem_from_metadata_strings(
         GRPC_MDSTR_AUTHORITY, GRPC_MDSTR_REF(md->value));
-    GRPC_MDELEM_UNREF(md);
     calld->seen_authority = 1;
     return authority;
   } else {

test/core/bad_client/tests/simple_request.c

@@ -55,6 +55,21 @@
   "\x10\x02te\x08trailers"                                                 \
   "\x10\x0auser-agent\"bad-client grpc-c/0.12.0.0 (linux)"
 
+#define PFX_STR_UNUSUAL                                                    \
+  "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"                                       \
+  "\x00\x00\x00\x04\x00\x00\x00\x00\x00" /* settings frame */              \
+  "\x00\x00\xd1\x01\x04\x00\x00\x00\x01" /* headers: generated from        \
+                                            simple_request_unusual.headers \
+                                            in this directory */           \
+  "\x10\x05:path\x08/foo/bar"                                              \
+  "\x10\x07:scheme\x04http"                                                \
+  "\x10\x07:method\x04POST"                                                \
+  "\x10\x04host\x09localhost"                                              \
+  "\x10\x0c""content-type\x1e""application/grpc+this-is-valid"             \
+  "\x10\x14grpc-accept-encoding\x15identity,deflate,gzip"                  \
+  "\x10\x02te\x08trailers"                                                 \
+  "\x10\x0auser-agent\"bad-client grpc-c/0.12.0.0 (linux)"
+
 static void *tag(gpr_intptr t) { return (void *)t; }
 
 static void verifier(grpc_server *server, grpc_completion_queue *cq) {
@@ -87,6 +102,7 @@ int main(int argc, char **argv) {
 
   /* basic request: check that things are working */
   GRPC_RUN_BAD_CLIENT_TEST(verifier, PFX_STR, 0);
+  GRPC_RUN_BAD_CLIENT_TEST(verifier, PFX_STR_UNUSUAL, 0);
 
   /* push an illegal data frame */
   GRPC_RUN_BAD_CLIENT_TEST(verifier, PFX_STR

test/core/bad_client/tests/simple_request_unusual.headers

+# headers used in simple_request.c
+# use tools/codegen/core/gen_header_frame.py to generate the binary strings
+# contained in the source code
+:path: /foo/bar
+:scheme: http
+:method: POST
+host: localhost
+content-type: application/grpc+this-is-valid
+grpc-accept-encoding: identity,deflate,gzip
+te: trailers
+user-agent: bad-client grpc-c/0.12.0.0 (linux)