Update local BaseScrollBar::contents_scroll_offset_ on Update.

ui/views/controls/scrollbar/base_scroll_bar.cc

 // Copyright (c) 2012 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 "ui/views/controls/scrollbar/base_scroll_bar.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
@@ skipping 370 matching lines @@
       break;
     case ScrollBarContextMenuCommand_ScrollNext:
       ScrollByAmount(SCROLL_NEXT_LINE);
       break;
   }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // BaseScrollBar, ScrollBar implementation:
 
-void BaseScrollBar::Update(int viewport_size, int content_size,
+void BaseScrollBar::Update(int viewport_size,
+                           int content_size,
                            int contents_scroll_offset) {
   ScrollBar::Update(viewport_size, content_size, contents_scroll_offset);
 
   // Make sure contents_size is always > 0 to avoid divide by zero errors in
   // calculations throughout this code.
   contents_size_ = std::max(1, content_size);
 
   viewport_size_ = std::max(1, viewport_size);
 
   if (content_size < 0)
     content_size = 0;
   if (contents_scroll_offset < 0)
     contents_scroll_offset = 0;
   if (contents_scroll_offset > content_size)
     contents_scroll_offset = content_size;
+  contents_scroll_offset_ = contents_scroll_offset;
 
   // Thumb Height and Thumb Pos.
   // The height of the thumb is the ratio of the Viewport height to the
   // content size multiplied by the height of the thumb track.
   double ratio = static_cast<double>(viewport_size) / contents_size_;
   int thumb_size = static_cast<int>(ratio * GetTrackSize());
   thumb_->SetSize(thumb_size);
 
   int thumb_position = CalculateThumbPosition(contents_scroll_offset);
   thumb_->SetPosition(thumb_position);
@@ skipping 74 matching lines @@
   // simple division can be rounded and there could be 1 pixel gap even when the
   // contents scroll down to the bottom. See crbug.com/244671
   if (contents_scroll_offset + viewport_size_ == contents_size_) {
     int track_size = GetTrackSize();
     return track_size - (viewport_size_ * GetTrackSize() / contents_size_);
   }
   return (contents_scroll_offset * GetTrackSize()) / contents_size_;
 }
 
 int BaseScrollBar::CalculateContentsOffset(int thumb_position,
-                                             bool scroll_to_middle) const {
+                                           bool scroll_to_middle) const {
   if (scroll_to_middle)
     thumb_position = thumb_position - (thumb_->GetSize() / 2);
   return (thumb_position * contents_size_) / GetTrackSize();
 }
 
 void BaseScrollBar::SetThumbTrackState(CustomButton::ButtonState state) {
   thumb_track_state_ = state;
   SchedulePaint();
 }
 
 }  // namespace views