Assert that convertToLength succeeds instead of returning Length(Undefined)

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 193 matching lines @@
     Length secondLength;
 
     if (Pair* pair = primitiveValue->getPairValue()) {
         firstLength = pair->first()->convertToLength<AnyConversion>(cssToLengthConversionData());
         secondLength = pair->second()->convertToLength<AnyConversion>(cssToLengthConversionData());
     } else {
         firstLength = primitiveValue->convertToLength<AnyConversion>(cssToLengthConversionData());
         secondLength = Length();
     }
 
-    if (firstLength.isUndefined() || secondLength.isUndefined())
-        return;
-
     b.setWidth(firstLength);
     b.setHeight(secondLength);
     layer->setSizeLength(b);
 }
 
 void CSSToStyleMap::mapFillXPosition(CSSPropertyID propertyID, FillLayer* layer, CSSValue* value) const
 {
     if (!value->isPrimitiveValue())
         return;
 
     CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
     Pair* pair = primitiveValue->getPairValue();
     if (pair) {
         ASSERT_UNUSED(propertyID, propertyID == CSSPropertyBackgroundPositionX || propertyID == CSSPropertyWebkitMaskPositionX);
         primitiveValue = pair->second();
     }
 
     Length length = primitiveValue->convertToLength<FixedConversion | PercentConversion>(cssToLengthConversionData());
-    ASSERT(!length.isUndefined());
 
     layer->setXPosition(length);
     if (pair)
         layer->setBackgroundXOrigin(*(pair->first()));
 }
 
 void CSSToStyleMap::mapFillYPosition(CSSPropertyID propertyID, FillLayer* layer, CSSValue* value) const
 {
     if (!value->isPrimitiveValue())
         return;
 
     CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
     Pair* pair = primitiveValue->getPairValue();
     if (pair) {
         ASSERT_UNUSED(propertyID, propertyID == CSSPropertyBackgroundPositionY || propertyID == CSSPropertyWebkitMaskPositionY);
         primitiveValue = pair->second();
     }
 
     Length length = primitiveValue->convertToLength<FixedConversion | PercentConversion>(cssToLengthConversionData());
-    ASSERT(!length.isUndefined());
 
     layer->setYPosition(length);
     if (pair)
         layer->setBackgroundYOrigin(*(pair->first()));
 }
 
 void CSSToStyleMap::mapFillMaskSourceType(CSSPropertyID, FillLayer* layer, CSSValue* value)
 {
     EMaskSourceType type = FillLayer::initialFillMaskSourceType(layer->type());
     if (value->isInitialValue()) {
@@ skipping 385 matching lines @@
         verticalRule = SpaceImageRule;
         break;
     default: // CSSValueRepeat
         verticalRule = RepeatImageRule;
         break;
     }
     image.setVerticalRule(verticalRule);
 }
 
 };