chrome: Cleanup class/struct forward declarations

chrome/test/base/chrome_render_view_host_test_harness.h

 // 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.
 
 #ifndef CHROME_TEST_BASE_CHROME_RENDER_VIEW_HOST_TEST_HARNESS_H_
 #define CHROME_TEST_BASE_CHROME_RENDER_VIEW_HOST_TEST_HARNESS_H_
 
 #include "base/compiler_specific.h"
 #include "content/public/test/test_renderer_host.h"
 
 class TestingProfile;
 
-namespace content {
-class WebContents;
-}
-
 // Wrapper around RenderViewHostTestHarness that uses a TestingProfile as
 // browser context instead of a TestBrowserContext.
 class ChromeRenderViewHostTestHarness
     : public content::RenderViewHostTestHarness {
  public:
   ChromeRenderViewHostTestHarness();
   ~ChromeRenderViewHostTestHarness() override;
 
   TestingProfile* profile();
 
  protected:
   // testing::Test
   void TearDown() override;
 
   // content::RenderViewHostTestHarness.
   content::BrowserContext* CreateBrowserContext() override;
 };
 
 #endif  // CHROME_TEST_BASE_CHROME_RENDER_VIEW_HOST_TEST_HARNESS_H_