If possible, use the PathService instead of the --user-data-dir flag directly

cloud_print/service/win/chrome_launcher.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 "cloud_print/service/win/chrome_launcher.h"
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
+#include "base/path_service.h"
 #include "base/process/process.h"
 #include "base/process/process.h"
 #include "base/values.h"
 #include "base/win/registry.h"
 #include "base/win/scoped_handle.h"
 #include "base/win/scoped_process_information.h"
 #include "chrome/common/chrome_constants.h"
+#include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/installer/launcher_support/chrome_launcher_support.h"
 #include "cloud_print/common/win/cloud_print_utils.h"
 #include "cloud_print/service/service_constants.h"
 #include "cloud_print/service/win/service_utils.h"
 #include "components/cloud_devices/common/cloud_devices_urls.h"
 #include "google_apis/gaia/gaia_urls.h"
 #include "net/base/url_util.h"
 #include "url/gurl.h"
@@ skipping 118 matching lines @@
   base::FilePath abs_user_data_dir = base::MakeAbsoluteFilePath(user_data_dir);
 
   {
     base::win::RegistryValueIterator value(HKEY_CURRENT_USER, kAutoRunKeyPath);
     for (; value.Valid(); ++value) {
       if (value.Type() == REG_SZ && value.Value()) {
         base::CommandLine cmd = base::CommandLine::FromString(value.Value());
         if (cmd.GetSwitchValueASCII(switches::kProcessType) ==
             switches::kServiceProcess &&
             cmd.HasSwitch(switches::kUserDataDir)) {
-          base::FilePath path_from_reg = base::MakeAbsoluteFilePath(
-              cmd.GetSwitchValuePath(switches::kUserDataDir));

[grt (UTC plus 2), 2015/03/26 18:36:22]

i wouldn't touch this one. it seems to me that cloud_print_service.exe is its
own thing with its own user data dir. it doesn't appear to register the chrome
path provider, so chrome::DIR_USER_DATA won't work.

[noms (inactive), 2015/03/30 14:06:33]

Done.

+          base::FilePath dir;
+          PathService::Get(chrome::DIR_USER_DATA, &dir);
+          base::FilePath path_from_reg = base::MakeAbsoluteFilePath(dir);
           if (path_from_reg == abs_user_data_dir) {
             to_delete.push_back(value.Name());
           }
         }
       }
     }
   }
 
   for (size_t i = 0; i < to_delete.size(); ++i) {
     key.DeleteValue(to_delete[i].c_str());
@@ skipping 151 matching lines @@
       LOG(ERROR) << "Chrome launch failed.";
       return std::string();
     }
     if (!json.empty()) {
       // Close chrome because Service State is ready.
       CloseChrome(chrome_process.Pass(), thread_id);
       return json;
     }
   }
 }