When moving past a left-hand scrollbar, don't jump way outside the content box.

third_party/WebKit/Source/core/layout/LayoutBlockFlowLine.cpp

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc.
  *               All right reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 736 matching lines @@
         UpdateLogicalWidthForRightAlignedBlock(
             Style()->IsLeftToRightDirection(), trailing_space_run, logical_left,
             total_logical_width, available_logical_width);
       else
         UpdateLogicalWidthForLeftAlignedBlock(
             Style()->IsLeftToRightDirection(), trailing_space_run, logical_left,
             total_logical_width, available_logical_width);
       break;
   }
   if (ShouldPlaceBlockDirectionScrollbarOnLogicalLeft())
-    logical_left += VerticalScrollbarWidth();
+    logical_left += VerticalScrollbarWidthClampedToContentBox();
 }
 
 static void UpdateLogicalInlinePositions(LayoutBlockFlow* block,
                                          LayoutUnit& line_logical_left,
                                          LayoutUnit& line_logical_right,
                                          LayoutUnit& available_logical_width,
                                          bool first_line,
                                          IndentTextOrNot indent_text,
                                          LayoutUnit box_logical_height) {
   LayoutUnit line_logical_height =
@@ skipping 1883 matching lines @@
 
 bool LayoutBlockFlow::PaintedOutputOfObjectHasNoEffectRegardlessOfSize() const {
   // LayoutBlockFlow is in charge of paint invalidation of the first line.
   if (FirstLineBox())
     return false;
 
   return LayoutBlock::PaintedOutputOfObjectHasNoEffectRegardlessOfSize();
 }
 
 }  // namespace blink