Remove explicit bounds check from CSSValueList::item

Source/core/css/resolver/CSSToStyleMap.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 445 matching lines @@
 
     for (unsigned i = 0 ; i < borderImage->length() ; ++i) {
         CSSValue* current = borderImage->item(i);
 
         if (current->isImageValue() || current->isImageGeneratorValue() || current->isImageSetValue())
             image.setImage(styleImage(imageProperty, current));
         else if (current->isBorderImageSliceValue())
             mapNinePieceImageSlice(current, image);
         else if (current->isValueList()) {
             CSSValueList* slashList = toCSSValueList(current);
+            size_t length = slashList->length();
             // Map in the image slices.
-            if (slashList->item(0) && slashList->item(0)->isBorderImageSliceValue())
+            if (length && slashList->item(0)->isBorderImageSliceValue())
                 mapNinePieceImageSlice(slashList->item(0), image);
 
             // Map in the border slices.
-            if (slashList->item(1))
+            if (length > 1)
                 image.setBorderSlices(mapNinePieceImageQuad(slashList->item(1)));
 
             // Map in the outset.
-            if (slashList->item(2))
+            if (length > 2)
                 image.setOutset(mapNinePieceImageQuad(slashList->item(2)));
         } else if (current->isPrimitiveValue()) {
             // Set the appropriate rules for stretch/round/repeat of the slices.
             mapNinePieceImageRepeat(current, image);
         }
     }
 
     if (property == CSSPropertyWebkitBorderImage) {
         // We have to preserve the legacy behavior of -webkit-border-image and make the border slices
         // also set the border widths. We don't need to worry about percentages, since we don't even support
@@ skipping 110 matching lines @@
         verticalRule = SpaceImageRule;
         break;
     default: // CSSValueRepeat
         verticalRule = RepeatImageRule;
         break;
     }
     image.setVerticalRule(verticalRule);
 }
 
 };