LayoutBox::scrollRectToVisible doesn't respect overflow:hidden property.

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

 /**
  * Copyright (C) 2006, 2007, 2010 Apple Inc. All rights reserved.
  *           (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
  *
  * 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 341 matching lines @@
 }
 
 PassRefPtr<ComputedStyle> LayoutTextControlSingleLine::createInnerEditorStyle(const ComputedStyle& startStyle) const
 {
     RefPtr<ComputedStyle> textBlockStyle = ComputedStyle::create();
     textBlockStyle->inheritFrom(startStyle);
     adjustInnerEditorStyle(*textBlockStyle);
 
     textBlockStyle->setWhiteSpace(PRE);
     textBlockStyle->setOverflowWrap(NormalOverflowWrap);
-    textBlockStyle->setOverflowX(OHIDDEN);
-    textBlockStyle->setOverflowY(OHIDDEN);
+    // Note that although overflowX/Y is set to scroll, the scrollbars will be
+    // hidden by the webkit-scrollbar selector in the default style sheet (html.css).
+    textBlockStyle->setOverflowX(OSCROLL);
+    textBlockStyle->setOverflowY(OSCROLL);
     textBlockStyle->setTextOverflow(textShouldBeTruncated() ? TextOverflowEllipsis : TextOverflowClip);
 
     if (m_desiredInnerEditorLogicalHeight >= 0)
         textBlockStyle->setLogicalHeight(Length(m_desiredInnerEditorLogicalHeight, Fixed));
     // Do not allow line-height to be smaller than our default.
     if (textBlockStyle->fontMetrics().lineSpacing() > lineHeight(true, HorizontalLine, PositionOfInteriorLineBoxes))
         textBlockStyle->setLineHeight(ComputedStyle::initialLineHeight());
 
     textBlockStyle->setDisplay(BLOCK);
     textBlockStyle->setUnique();
@@ skipping 65 matching lines @@
     if (innerEditorElement())
         innerEditorElement()->setScrollTop(newTop);
 }
 
 HTMLInputElement* LayoutTextControlSingleLine::inputElement() const
 {
     return toHTMLInputElement(node());
 }
 
 }