Add a new priority level, THROTTLED, below IDLE.

net/quic/quic_http_utils.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_http_utils.h"
 
 #include <utility>
 
 namespace net {
 
 SpdyPriority ConvertRequestPriorityToQuicPriority(
     const RequestPriority priority) {
   DCHECK_GE(priority, MINIMUM_PRIORITY);
   DCHECK_LE(priority, MAXIMUM_PRIORITY);
-  return static_cast<SpdyPriority>(HIGHEST - priority);
+  return static_cast<SpdyPriority>(MAXIMUM_PRIORITY - priority +
+                                   kV3HighestPriority);
 }
 
 NET_EXPORT_PRIVATE RequestPriority
 ConvertQuicPriorityToRequestPriority(SpdyPriority priority) {
   // Handle invalid values gracefully.
-  return (priority >= 5) ? IDLE
-                         : static_cast<RequestPriority>(HIGHEST - priority);
+  return ((priority - kV3HighestPriority) >
+                  (MAXIMUM_PRIORITY - MINIMUM_PRIORITY)
+              ? IDLE
+              : static_cast<RequestPriority>(MAXIMUM_PRIORITY -
+                                             (priority - kV3HighestPriority)));
 }
 
 std::unique_ptr<base::Value> QuicRequestNetLogCallback(
     QuicStreamId stream_id,
     const SpdyHeaderBlock* headers,
     SpdyPriority priority,
     NetLogCaptureMode capture_mode) {
   std::unique_ptr<base::DictionaryValue> dict(
       static_cast<base::DictionaryValue*>(
           SpdyHeaderBlockNetLogCallback(headers, capture_mode).release()));
   dict->SetInteger("quic_priority", static_cast<int>(priority));
   dict->SetInteger("quic_stream_id", static_cast<int>(stream_id));
   return std::move(dict);
 }
 
 }  // namespace net