Closing a guest session clears all browsing history.

chrome/test/base/testing_profile.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/test/base/testing_profile.h"
 
 #include "base/base_paths.h"
 #include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop_proxy.h"
@@ skipping 827 matching lines @@
 }
 
 net::URLRequestContextGetter* TestingProfile::GetRequestContextForRenderProcess(
     int renderer_child_id) {
   content::RenderProcessHost* rph = content::RenderProcessHost::FromID(
       renderer_child_id);
   return rph->GetStoragePartition()->GetURLRequestContext();
 }
 
 net::URLRequestContextGetter* TestingProfile::GetMediaRequestContext() {
-  return NULL;
+  // We don't test the media context here yet, so returning the same dummy
+  // context is sufficient for now.
+  return GetRequestContext();
 }
 
 net::URLRequestContextGetter*
 TestingProfile::GetMediaRequestContextForRenderProcess(
     int renderer_child_id) {
   return NULL;
 }
 
 net::URLRequestContextGetter*
 TestingProfile::GetMediaRequestContextForStoragePartition(
@@ skipping 225 matching lines @@
 #if defined(ENABLE_EXTENSIONS)
                             extension_policy_,
 #endif
                             pref_service_.Pass(),
                             original_profile,
                             guest_session_,
                             supervised_user_id_,
                             policy_service_.Pass(),
                             testing_factories_);
 }