Remove unused paintScrollbarThumb impl.

content/shell/renderer/test_runner/mock_web_theme_engine_mac.h

-// 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.
-
-#ifndef CONTENT_SHELL_RENDERER_TEST_RUNNER_MOCK_WEB_THEME_ENGINE_MAC_H_
-#define CONTENT_SHELL_RENDERER_TEST_RUNNER_MOCK_WEB_THEME_ENGINE_MAC_H_
-
-#include "base/macros.h"
-#include "third_party/WebKit/public/platform/WebThemeEngine.h"
-
-namespace content {
-
-// This implements the WebThemeEngine API in such a way that we match the Mac
-// port rendering more than usual Chromium path, thus allowing us to share
-// more pixel baselines.
-class MockWebThemeEngineMac : public blink::WebThemeEngine {
- public:
-  MockWebThemeEngineMac() {}
-  virtual ~MockWebThemeEngineMac() {}
-
-  virtual void paintScrollbarThumb(blink::WebCanvas*,
-                                   blink::WebThemeEngine::State,
-                                   blink::WebThemeEngine::Size,
-                                   const blink::WebRect&,
-                                   const blink::WebThemeEngine::ScrollbarInfo&);
-
- private:
-  virtual void paintHIThemeScrollbarThumb(
-      blink::WebCanvas*,
-      blink::WebThemeEngine::State,
-      blink::WebThemeEngine::Size,
-      const blink::WebRect&,
-      const blink::WebThemeEngine::ScrollbarInfo&);
-  virtual void paintNSScrollerScrollbarThumb(
-      blink::WebCanvas*,
-      blink::WebThemeEngine::State,
-      blink::WebThemeEngine::Size,
-      const blink::WebRect&,
-      const blink::WebThemeEngine::ScrollbarInfo&);
-
-  DISALLOW_COPY_AND_ASSIGN(MockWebThemeEngineMac);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_SHELL_RENDERER_TEST_RUNNER_MOCK_WEB_THEME_ENGINE_MAC_H_