Fix flaky test ContentSerializedNavigationBuilderTest.ToNavigationEntry

components/sessions/content/content_serialized_navigation_driver.cc

 // Copyright 2014 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 "components/sessions/content/content_serialized_navigation_driver.h"
 
 #include "base/memory/singleton.h"
 #include "build/build_config.h"
 #include "components/sessions/core/serialized_navigation_entry.h"
 #include "content/public/common/page_state.h"
@@ skipping 144 matching lines @@
   DCHECK(!extended_info_handler_map_.count(key));
   DCHECK(handler.get());
   extended_info_handler_map_[key] = std::move(handler);
 }
 
 const ContentSerializedNavigationDriver::ExtendedInfoHandlerMap&
 ContentSerializedNavigationDriver::GetAllExtendedInfoHandlers() const {
   return extended_info_handler_map_;
 }
 
+void ContentSerializedNavigationDriver::
+RemoveAllExtendedInfoHandlersForTesting() {
+  extended_info_handler_map_.clear();
+}
+
 }  // namespace sessions