It seems GAIA had changed dosserver rules today, so we can go back to accounts.google.com.

chrome/common/net/url_util.cc

 // 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.
 
 #include "chrome/common/net/url_util.h"
 
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/common/url_constants.h"
 #include "googleurl/src/gurl.h"
@@ skipping 29 matching lines @@
   if (!query.empty())
     query += "&";
 
   query += (net::EscapeQueryParamValue(name, true) + "=" +
             net::EscapeQueryParamValue(value, true));
   GURL::Replacements replacements;
   replacements.SetQueryStr(query);
   return url.ReplaceComponents(replacements);
 }
 
-
 GURL AppendOrReplaceQueryParameter(const GURL& url,
                                    const std::string& name,
                                    const std::string& value) {
   bool replaced = false;
   std::string param_name = net::EscapeQueryParamValue(name, true);
   std::string param_value = net::EscapeQueryParamValue(value, true);
 
   const std::string input = url.query();
   url_parse::Component cursor(0, input.size());
   std::string output;
@@ skipping 23 matching lines @@
     if (!output.empty())
       output += "&";
 
     output += (param_name + "=" + param_value);
   }
   GURL::Replacements replacements;
   replacements.SetQueryStr(output);
   return url.ReplaceComponents(replacements);
 }
 
+bool GetValueForKeyInQuery(const GURL& url,
+                           const std::string& search_key,
+                           std::string* out_value) {
+  url_parse::Component query = url.parsed_for_possibly_invalid_spec().query;
+  url_parse::Component key, value;
+  while (url_parse::ExtractQueryKeyValue(
+      url.spec().c_str(), &query, &key, &value)) {
+    if (key.is_nonempty()) {
+      std::string key_string = url.spec().substr(key.begin, key.len);
+      if (key_string == search_key) {
+        if (value.is_nonempty()) {
+          *out_value = net::UnescapeURLComponent(
+              url.spec().substr(value.begin, value.len),
+              net::UnescapeRule::SPACES |
+                  net::UnescapeRule::URL_SPECIAL_CHARS |
+                  net::UnescapeRule::REPLACE_PLUS_WITH_SPACE);
+        } else {
+          *out_value = "";
+        }
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
 }  // namespace chrome_common_net