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

chrome/app/chrome_main_delegate.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/app/chrome_main_delegate.h"
 
 #include "base/base_paths.h"
 #include "base/command_line.h"
 #include "base/cpu.h"
 #include "base/files/file_path.h"
@@ skipping 327 matching lines @@
       user_data_dir = base::FilePath::FromUTF8Unsafe(user_data_dir_string);
     }
   }
 #endif
 #if defined(OS_MACOSX) || defined(OS_WIN)
   policy::path_parser::CheckUserDataDirPolicy(&user_data_dir);
 #endif
 
   // On Windows, trailing separators leave Chrome in a bad state.
   // See crbug.com/464616.
-  if (user_data_dir.EndsWithSeparator()) {
+  if (user_data_dir.EndsWithSeparator())
     user_data_dir = user_data_dir.StripTrailingSeparators();
-    command_line->AppendSwitchPath(switches::kUserDataDir, user_data_dir);
-  }
 
   const bool specified_directory_was_invalid = !user_data_dir.empty() &&
       !PathService::OverrideAndCreateIfNeeded(chrome::DIR_USER_DATA,
           user_data_dir, false, true);
   // Save inaccessible or invalid paths so the user may be prompted later.
   if (specified_directory_was_invalid)
     chrome::SetInvalidSpecifiedUserDataDir(user_data_dir);
 
   // Warn and fail early if the process fails to get a user data directory.
   if (!PathService::Get(chrome::DIR_USER_DATA, &user_data_dir)) {
@@ skipping 598 matching lines @@
     case chrome::VersionInfo::CHANNEL_CANARY:
       return true;
     case chrome::VersionInfo::CHANNEL_DEV:
     case chrome::VersionInfo::CHANNEL_BETA:
     case chrome::VersionInfo::CHANNEL_STABLE:
     default:
       // Don't enable instrumentation.
       return false;
   }
 }