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

ppapi/tests/test_scrollbar.cc

 // 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.
 
 #include "ppapi/tests/test_scrollbar.h"
 
 #include <cstring>
 
 #include "ppapi/c/dev/ppb_testing_dev.h"
 #include "ppapi/c/pp_input_event.h"
@@ skipping 42 matching lines @@
 
 void TestScrollbar::InvalidateWidget(pp::Widget_Dev widget,
                                      const pp::Rect& dirty_rect) {
 }
 
 void TestScrollbar::ScrollbarValueChanged(pp::Scrollbar_Dev scrollbar,
                                           uint32_t value) {
   if (scrollbar == scrollbar_)
     scrollbar_value_changed_ = true;
 }
+
+void TestScrollbar::ScrollbarOverlayChanged(pp::Scrollbar_Dev scrollbar,
+                                            bool type) {
+}