Update some comments in url_request.h to clarify that once the request is del...

net/url_request/url_request.h

 // Copyright (c) 2006-2008 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_URL_REQUEST_URL_REQUEST_H_
 #define NET_URL_REQUEST_URL_REQUEST_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 359 matching lines @@
   // error.  Otherwise, it is a value defined by the operating system (e.g., an
   // error code returned by GetLastError() on windows).
   const URLRequestStatus& status() const { return status_; }
 
   // This method is called to start the request.  The delegate will receive
   // a OnResponseStarted callback when the request is started.
   void Start();
 
   // This method may be called at any time after Start() has been called to
   // cancel the request.  This method may be called many times, and it has
-  // no effect once the response has completed.
+  // no effect once the response has completed.  It is guaranteed that no
+  // methods of the delegate will be called after the request has been
+  // cancelled, including during the call to Cancel itself.
   void Cancel();
 
   // Cancels the request and sets the error to |os_error| (see net_error_list.h
   // for values).
   void SimulateError(int os_error);
 
   // Cancels the request and sets the error to |os_error| (see net_error_list.h
   // for values) and attaches |ssl_info| as the SSLInfo for that request.  This
   // is useful to attach a certificate and certificate error to a canceled
   // request.
   void SimulateSSLError(int os_error, const net::SSLInfo& ssl_info);
 
   // Read initiates an asynchronous read from the response, and must only
   // be called after the OnResponseStarted callback is received with a
   // successful status.
   // If data is available, Read will return true, and the data and length will
   // be returned immediately.  If data is not available, Read returns false,
   // and an asynchronous Read is initiated.  The Read is finished when
-  // the caller receives the OnReadComplete callback.  OnReadComplete will be
-  // always be called, even if there was a failure.
+  // the caller receives the OnReadComplete callback.  Unless the request was
+  // cancelled, OnReadComplete will always be called, even if the read failed.
   //
   // The buf parameter is a buffer to receive the data.  If the operation
   // completes asynchronously, the implementation will reference the buffer
   // until OnReadComplete is called.  The buffer must be at least max_bytes in
   // length.
   //
   // The max_bytes parameter is the maximum number of bytes to read.
   //
   // The bytes_read parameter is an output parameter containing the
   // the number of bytes read.  A value of 0 indicates that there is no
@@ skipping 159 matching lines @@
 #define URLREQUEST_COUNT_DTOR() url_request_metrics.object_count--
 
 #else  // disable leak checking in release builds...
 
 #define URLREQUEST_COUNT_CTOR()
 #define URLREQUEST_COUNT_DTOR()
 
 #endif  // #ifndef NDEBUG
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_H_