Revert of Change minimum length of Aura overlay scrollbars.

third_party/WebKit/Source/platform/scroll/ScrollbarTheme.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 341 matching lines @@
 
   return thumbRect;
 }
 
 int ScrollbarTheme::thumbThickness(const ScrollbarThemeClient& scrollbar) {
   IntRect track = trackRect(scrollbar);
   return scrollbar.orientation() == HorizontalScrollbar ? track.height()
                                                         : track.width();
 }
 
+int ScrollbarTheme::minimumThumbLength(const ScrollbarThemeClient& scrollbar) {
+  return scrollbarThickness(scrollbar.controlSize());
+}
+
 void ScrollbarTheme::splitTrack(const ScrollbarThemeClient& scrollbar,
                                 const IntRect& unconstrainedTrackRect,
                                 IntRect& beforeThumbRect,
                                 IntRect& thumbRect,
                                 IntRect& afterThumbRect) {
   // This function won't even get called unless we're big enough to have some
   // combination of these three rects where at least one of them is non-empty.
   IntRect trackRect =
       constrainTrackRectToTrackPieces(scrollbar, unconstrainedTrackRect);
   int thumbPos = thumbPosition(scrollbar);
@@ skipping 62 matching lines @@
       return DisplayItem::kScrollbarBackTrack;
     case ForwardTrackPart:
       return DisplayItem::kScrollbarForwardTrack;
     default:
       ASSERT_NOT_REACHED();
       return DisplayItem::kScrollbarBackTrack;
   }
 }
 
 }  // namespace blink