Pepper and WebKit API change to support a plugin knowing if a scrollbar is an overlay one.

ppapi/thunk/ppb_scrollbar_group_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_GROUP_API_H_
+#define PPAPI_THUNK_PPB_SCROLLBAR_GROUP_API_H_
+
+#include "ppapi/c/dev/ppb_scrollbar_group_dev.h"
+
+namespace ppapi {
+namespace thunk {
+
+class PPB_ScrollbarGroup_API {
+ public:
+  virtual ~PPB_ScrollbarGroup_API() {}
+
+  virtual void MouseEnteredContentArea() = 0;
+  virtual void MouseMovedInContentArea() = 0;
+  virtual void MouseExitedContentArea() = 0;
+  virtual void WillStartLiveResize() = 0;
+  virtual void ContentResized() = 0;
+  virtual void WillEndLiveResize() = 0;
+};
+
+}  // namespace thunk
+}  // namespace ppapi
+
+#endif  // PPAPI_THUNK_PPB_SCROLLBAR_GROUP_API_H_