Update comments about scrollbar thickness.

third_party/WebKit/Source/core/layout/LayoutThemeDefault.h

 /*
  * This file is part of the WebKit project.
  *
  * Copyright (C) 2006 Apple Computer, Inc.
  * Copyright (C) 2006 Michael Emmel mike.emmel@gmail.com
  * Copyright (C) 2007 Holger Hans Peter Freyther
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2008, 2009 Google, Inc.
  * All rights reserved.
  * Copyright (C) 2009 Kenneth Rohde Christiansen
@@ skipping 97 matching lines @@
 
   double animationRepeatIntervalForProgressBar() const override;
   double animationDurationForProgressBar() const override;
 
   // These methods define the padding for the MenuList's inner block.
   int popupInternalPaddingStart(const ComputedStyle&) const override;
   int popupInternalPaddingEnd(const HostWindow*,
                               const ComputedStyle&) const override;
   int popupInternalPaddingTop(const ComputedStyle&) const override;
   int popupInternalPaddingBottom(const ComputedStyle&) const override;
-  int scrollbarThicknessInDIP() const;
+  // This returns a value based on scrollbar thickness.  It's not 0 even in
+  // overlay scrollbar mode.  On Android, this doesn't match to scrollbar
+  // thickness, which is 3px or 4px, and we use the value from the default Aura
+  // theme.
+  int menuListArrowWidthInDIP() const;
   float clampedMenuListArrowPaddingSize(const HostWindow*,
                                         const ComputedStyle&) const;
 
   // Provide a way to pass the default font size from the Settings object
   // to the layout theme. FIXME: http://b/1129186 A cleaner way would be
   // to remove the default font size from this object and have callers
   // that need the value to get it directly from the appropriate Settings
   // object.
   static void setDefaultFontSize(int);
 
@@ skipping 19 matching lines @@
 
   static const RGBA32 defaultTapHighlightColor = 0x2e000000;  // 18% black.
   static double m_caretBlinkInterval;
 
   static unsigned m_activeSelectionBackgroundColor;
   static unsigned m_activeSelectionForegroundColor;
   static unsigned m_inactiveSelectionBackgroundColor;
   static unsigned m_inactiveSelectionForegroundColor;
 
   ThemePainterDefault m_painter;
-  int m_scrollbarThicknessInDIP = 0;
+  int m_menuListArrowWidthInDIP = 0;
 };
 
 }  // namespace blink
 
 #endif  // LayoutThemeDefault_h