Remove unused in-process pepper APIs

ppapi/thunk/ppb_scrollbar_api.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 PPAPI_THUNK_PPB_SCROLLBAR_API_H_
-#define PPAPI_THUNK_PPB_SCROLLBAR_API_H_
-
-#include "ppapi/c/dev/ppb_scrollbar_dev.h"
-
-namespace ppapi {
-namespace thunk {
-
-class PPB_Scrollbar_API {
- public:
-  virtual ~PPB_Scrollbar_API() {}
-
-  virtual uint32_t GetThickness() = 0;
-  virtual bool IsOverlay() = 0;
-  virtual uint32_t GetValue() = 0;
-  virtual void SetValue(uint32_t value) = 0;
-  virtual void SetDocumentSize(uint32_t size) = 0;
-  virtual void SetTickMarks(const PP_Rect* tick_marks, uint32_t count) = 0;
-  virtual void ScrollBy(PP_ScrollBy_Dev unit, int32_t multiplier) = 0;
-};
-
-}  // namespace thunk
-}  // namespace ppapi
-
-#endif  // PPAPI_THUNK_PPB_SCROLLBAR_API_H_