allow unit_tests to re-create service manager context.

content/browser/child_process_launcher_helper_posix.cc

 // Copyright 2017 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 "content/browser/child_process_launcher_helper_posix.h"
 
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/posix/global_descriptors.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 123 matching lines @@
   if (!base::StartsWith(service_name, "content_",
                         base::CompareCase::INSENSITIVE_ASCII)) {
     // Not a content child service, ignore.
     return;
   }
 
   DCHECK(GetRequiredFilesByServiceMap().count(service_name) == 0);
   GetRequiredFilesByServiceMap()[service_name] = std::move(required_files);
 }
 
+void ResetFilesToShareForTestingPosix() {
+  GetRequiredFilesByServiceMap().clear();
+}
+
 }  // namespace internal
 }  // namespace content