Add detailed histograms for DownloadProtectionService URLFetcher errors.

net/url_request/url_request_status.h

 // Copyright (c) 2011 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 file's dependencies should be kept to a minimum so that it can be
 // included in WebKit code that doesn't rely on much of common.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_STATUS_H_
 #define NET_URL_REQUEST_URL_REQUEST_STATUS_H_
 
 namespace net {
 
 // Represents the result of a URL request. It encodes errors and various
 // types of success.
 class URLRequestStatus {
  public:
   enum Status {
     // Request succeeded, |error_| will be 0.
     SUCCESS = 0,
 
     // An IO request is pending, and the caller will be informed when it is
     // completed.
     IO_PENDING,
 
     // Request was cancelled programatically.
     CANCELED,
 
     // The request failed for some reason. |error_| may have more information.
     FAILED,
+
+    // So that Status enums can be used in histograms, always add new values
+    // before this one, and do not change existing values.
+    STATUS_MAX

[mattm, 2013/07/24 02:19:00]

any objections to this?

[mmenke, 2013/07/24 14:26:50]

Nope, I'm fine with it...  But I'm not sure we need it, per other comment.

   };
 
   URLRequestStatus() : status_(SUCCESS), error_(0) {}
   URLRequestStatus(Status s, int e) : status_(s), error_(e) {}
 
   Status status() const { return status_; }
   void set_status(Status s) { status_ = s; }
 
   int error() const { return error_; }
   void set_error(int e) { error_ = e; }
@@ skipping 13 matching lines @@
   // Application level status.
   Status status_;
 
   // Error code from the network layer if an error was encountered.
   int error_;
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_STATUS_H_