Implementation of network level throttler.

net/base/load_states_list.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.
 
 // This is the list of load states and their values. For the enum values,
 // include the file "net/base/load_states.h".
 //
 // Here we define the values using a macro LOAD_STATE, so it can be
 // expanded differently in some places (for example, to automatically
 // map a load flag value to its symbolic name).
 
 // This is the default state.  It corresponds to a resource load that has
 // either not yet begun or is idle waiting for the consumer to do something
 // to move things along (e.g., the consumer of an URLRequest may not have
 // called Read yet).
 LOAD_STATE(IDLE, 0)
 
+// This state corresponds to a resource load that is throttled by the
+// network layer waiting for some other resource load or loads to complete.
+LOAD_STATE(THROTTLED, 1)
+
 // When a socket pool group is below the maximum number of sockets allowed per
 // group, but a new socket cannot be created due to the per-pool socket limit,
 // this state is returned by all requests for the group waiting on an idle
 // connection, except those that may be serviced by a pending new connection.
-LOAD_STATE(WAITING_FOR_STALLED_SOCKET_POOL, 1)
+LOAD_STATE(WAITING_FOR_STALLED_SOCKET_POOL, 2)
 
 // When a socket pool group has reached the maximum number of sockets allowed
 // per group, this state is returned for all requests that don't have a socket,
 // except those that correspond to a pending new connection.
-LOAD_STATE(WAITING_FOR_AVAILABLE_SOCKET, 2)
+LOAD_STATE(WAITING_FOR_AVAILABLE_SOCKET, 3)
 
 // This state indicates that the URLRequest delegate has chosen to block this
 // request before it was sent over the network. When in this state, the
 // delegate should set a load state parameter on the URLRequest describing
 // the nature of the delay (i.e. "Waiting for <description given by
 // delegate>").
-LOAD_STATE(WAITING_FOR_DELEGATE, 3)
+LOAD_STATE(WAITING_FOR_DELEGATE, 4)
 
 // This state corresponds to a resource load that is blocked waiting for
 // access to a resource in the cache.  If multiple requests are made for the
 // same resource, the first request will be responsible for writing (or
 // updating) the cache entry and the second request will be deferred until
 // the first completes.  This may be done to optimize for cache reuse.
-LOAD_STATE(WAITING_FOR_CACHE, 4)
+LOAD_STATE(WAITING_FOR_CACHE, 5)
 
 // This state corresponds to a resource load that is blocked waiting for
 // access to a resource in the AppCache.
 // Note: This is a layering violation, but being the only one it's not that
 // bad. TODO(rvargas): Reconsider what to do if we need to add more.
-LOAD_STATE(WAITING_FOR_APPCACHE, 5)
+LOAD_STATE(WAITING_FOR_APPCACHE, 6)
 
 // This state corresponds to a resource being blocked waiting for the
 // PAC script to be downloaded.
-LOAD_STATE(DOWNLOADING_PROXY_SCRIPT, 6)
+LOAD_STATE(DOWNLOADING_PROXY_SCRIPT, 7)
 
 // This state corresponds to a resource load that is blocked waiting for a
 // proxy autoconfig script to return a proxy server to use.
-LOAD_STATE(RESOLVING_PROXY_FOR_URL, 7)
+LOAD_STATE(RESOLVING_PROXY_FOR_URL, 8)
 
 // This state corresponds to a resource load that is blocked waiting for a
 // proxy autoconfig script to return a proxy server to use, but that proxy
 // script is busy resolving the IP address of a host.
-LOAD_STATE(RESOLVING_HOST_IN_PROXY_SCRIPT, 8)
+LOAD_STATE(RESOLVING_HOST_IN_PROXY_SCRIPT, 9)
 
 // This state indicates that we're in the process of establishing a tunnel
 // through the proxy server.
-LOAD_STATE(ESTABLISHING_PROXY_TUNNEL, 9)
+LOAD_STATE(ESTABLISHING_PROXY_TUNNEL, 10)
 
 // This state corresponds to a resource load that is blocked waiting for a
 // host name to be resolved.  This could either indicate resolution of the
 // origin server corresponding to the resource or to the host name of a proxy
 // server used to fetch the resource.
-LOAD_STATE(RESOLVING_HOST, 10)
+LOAD_STATE(RESOLVING_HOST, 11)
 
 // This state corresponds to a resource load that is blocked waiting for a
 // TCP connection (or other network connection) to be established.  HTTP
 // requests that reuse a keep-alive connection skip this state.
-LOAD_STATE(CONNECTING, 11)
+LOAD_STATE(CONNECTING, 12)
 
 // This state corresponds to a resource load that is blocked waiting for the
 // SSL handshake to complete.
-LOAD_STATE(SSL_HANDSHAKE, 12)
+LOAD_STATE(SSL_HANDSHAKE, 13)
 
 // This state corresponds to a resource load that is blocked waiting to
 // completely upload a request to a server.  In the case of a HTTP POST
 // request, this state includes the period of time during which the message
 // body is being uploaded.
-LOAD_STATE(SENDING_REQUEST, 13)
+LOAD_STATE(SENDING_REQUEST, 14)
 
 // This state corresponds to a resource load that is blocked waiting for the
 // response to a network request.  In the case of a HTTP transaction, this
 // corresponds to the period after the request is sent and before all of the
 // response headers have been received.
-LOAD_STATE(WAITING_FOR_RESPONSE, 14)
+LOAD_STATE(WAITING_FOR_RESPONSE, 15)
 
 // This state corresponds to a resource load that is blocked waiting for a
 // read to complete.  In the case of a HTTP transaction, this corresponds to
 // the period after the response headers have been received and before all of
 // the response body has been downloaded.  (NOTE: This state only applies for
 // an URLRequest while there is an outstanding Read operation.)
-LOAD_STATE(READING_RESPONSE, 15)
+LOAD_STATE(READING_RESPONSE, 16)