Delete the NPAPI plugin browsertests.

content/test/plugin/plugin_npobject_proxy_test.h

-// Copyright (c) 2011 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.
-
-#ifndef CONTENT_TEST_PLUGIN_PLUGIN_NPOBJECT_PROXY_TEST_H_
-#define CONTENT_TEST_PLUGIN_PLUGIN_NPOBJECT_PROXY_TEST_H_
-
-#include "base/compiler_specific.h"
-#include "content/test/plugin/plugin_test.h"
-
-namespace NPAPIClient {
-
-// The NPObjectProxyTest tests that when we proxy an NPObject that is itself
-// a proxy, we don't create a new proxy but instead just use the original
-// pointer.
-
-class NPObjectProxyTest : public PluginTest {
- public:
-  // Constructor.
-  NPObjectProxyTest(NPP id, NPNetscapeFuncs *host_functions);
-
-  // NPAPI SetWindow handler.
-  NPError SetWindow(NPWindow* pNPWindow) override;
-};
-
-}  // namespace NPAPIClient
-
-#endif  // CONTENT_TEST_PLUGIN_PLUGIN_NPOBJECT_PROXY_TEST_H_