Clean up the Linux WebThemeEngine impl according to the coding style rules

webkit/glue/webthemeengine_impl_mac.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// 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 WEBKIT_GLUE_WEBTHEMEENGINE_IMPL_MAC_H_
 #define WEBKIT_GLUE_WEBTHEMEENGINE_IMPL_MAC_H_
 
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/mac/WebThemeEngine.h"
 
 namespace webkit_glue {
 
 class WebThemeEngineImpl : public WebKit::WebThemeEngine {
  public:
   // WebKit::WebThemeEngine implementation.
   virtual void paintScrollbarThumb(
-      WebKit::WebCanvas*,
-      WebKit::WebThemeEngine::State,
-      WebKit::WebThemeEngine::Size,
-      const WebKit::WebRect&,
-      const WebKit::WebThemeEngine::ScrollbarInfo&);
+      WebKit::WebCanvas* canvas,
+      WebKit::WebThemeEngine::State part,
+      WebKit::WebThemeEngine::Size state,
+      const WebKit::WebRect& rect,
+      const WebKit::WebThemeEngine::ScrollbarInfo& extra_params);
 };
 
 }  // namespace webkit_glue
 
 #endif  // WEBKIT_GLUE_WEBTHEMEENGINE_IMPL_MAC_H_