Use --gtest_flagfile for --gtest_filter in unit test launcher

base/test/launcher/test_launcher.cc

 // Copyright 2013 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 "base/test/launcher/test_launcher.h"
 
 #if defined(OS_POSIX)
 #include <fcntl.h>
 #endif
 
@@ skipping 418 matching lines @@
   // a worker pool thread.
   task_runner->PostTask(FROM_HERE, Bind(&RunCallback, callback, exit_code,
                                         TimeTicks::Now() - start_time,
                                         was_timeout, output_file_contents));
 }
 
 }  // namespace
 
 const char kGTestBreakOnFailure[] = "gtest_break_on_failure";
 const char kGTestFilterFlag[] = "gtest_filter";
+const char kGTestFlagfileFlag[] = "gtest_flagfile";
 const char kGTestHelpFlag[]   = "gtest_help";
 const char kGTestListTestsFlag[] = "gtest_list_tests";
 const char kGTestRepeatFlag[] = "gtest_repeat";
 const char kGTestRunDisabledTestsFlag[] = "gtest_also_run_disabled_tests";
 const char kGTestOutputFlag[] = "gtest_output";
 
 TestLauncherDelegate::~TestLauncherDelegate() {
 }
 
 TestLauncher::TestLauncher(TestLauncherDelegate* launcher_delegate,
@@ skipping 638 matching lines @@
   }
 
   std::string snippet(full_output.substr(run_pos));
   if (end_pos != std::string::npos)
     snippet = full_output.substr(run_pos, end_pos - run_pos);
 
   return snippet;
 }
 
 }  // namespace base