Add a new priority level, THROTTLED, below IDLE.

net/base/request_priority.h

 // Copyright (c) 2012 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.
 
 #ifndef NET_BASE_REQUEST_PRIORITY_H_
 #define NET_BASE_REQUEST_PRIORITY_H_
 
 #include "net/base/net_export.h"
 
 namespace net {
 
 // Prioritization used in various parts of the networking code such
 // as connection prioritization and resource loading prioritization.
 // A Java counterpart will be generated for this enum.
 // GENERATED_JAVA_ENUM_PACKAGE: org.chromium.net
 // GENERATED_JAVA_CLASS_NAME_OVERRIDE: RequestPriority
 // GENERATED_JAVA_PREFIX_TO_STRIP:
 enum RequestPriority {
-  IDLE = 0,
-  MINIMUM_PRIORITY = IDLE,
+  THROTTLED = 0,  // Used to signal that resources
+                  // should be reserved for following
+                  // requests (i.e. that higher priority
+                  // following requests are expected).
+  MINIMUM_PRIORITY = THROTTLED,
+  IDLE,  // Default "as resources available" level.
   LOWEST,
   DEFAULT_PRIORITY = LOWEST,
   LOW,
   MEDIUM,
   HIGHEST,
   MAXIMUM_PRIORITY = HIGHEST,
 };
 
 // For simplicity, one can assume that one can index into array of
 // NUM_PRIORITIES elements with a RequestPriority (i.e.,
 // MINIMUM_PRIORITY == 0).
 enum RequestPrioritySize {
   NUM_PRIORITIES = MAXIMUM_PRIORITY + 1,
 };
 
 NET_EXPORT const char* RequestPriorityToString(RequestPriority priority);
 
 }  // namespace net
 
 #endif  // NET_BASE_REQUEST_PRIORITY_H_