chrome::ShowTaskManager: refine return type to eliminate a downcast.

chrome/browser/task_management/task_manager_tester.cc

 // Copyright 2016 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/browser/task_management/task_manager_tester.h"
 
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_tab_helper.h"
@@ skipping 127 matching lines @@
 
   void Kill(int row) override { model_->KillTask(row); }
 
  private:
   task_management::TaskManagerInterface* task_manager() {
     return model_->observed_task_manager();
   }
 
   // Returns the TaskManagerTableModel for the the visible NewTaskManagerView.
   static task_management::TaskManagerTableModel* GetRealModel() {
-    // This downcast is safe, as long as the new task manager is enabled.
-    task_management::TaskManagerTableModel* result =
-        static_cast<task_management::TaskManagerTableModel*>(
-            chrome::ShowTaskManager(nullptr));
-    return result;
+    return chrome::ShowTaskManager(nullptr);
   }
 
   task_management::TaskManagerTableModel* model_;
   std::unique_ptr<ScopedInterceptTableModelObserver> interceptor_;
 };
 
 // static
 std::unique_ptr<TaskManagerTester> TaskManagerTester::CreateDefault(
     const base::Closure& callback) {
   return base::WrapUnique(new TaskManagerTesterImpl(callback));
 }
 
 }  // namespace task_management