[CSS Grid Layout] CSSParser should reject <track-list> without a <track-size>

Source/core/css/resolver/StyleResolver.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, 2013 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 2285 matching lines @@
         }
 
         ++currentNamedGridLine;
         GridTrackSize trackSize;
         if (!createGridTrackSize(currValue, trackSize, state))
             return false;
 
         trackSizes.append(trackSize);
     }
 
-    if (trackSizes.isEmpty())
-        return false;
-
+    // The parser should have rejected any <track-list> without any <track-size> as
+    // this is not conformant to the syntax.
+    ASSERT(!trackSizes.isEmpty());
     return true;
 }
 
 
 static bool createGridPosition(CSSValue* value, GridPosition& position)
 {
     // For now, we only accept: 'auto' | [ <integer> || <string> ] | span && <integer>?
 
     if (value->isPrimitiveValue()) {
         CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
@@ skipping 1393 matching lines @@
     info.addMember(m_state, "state");
 
     // FIXME: move this to a place where it would be called only once?
     info.addMember(CSSDefaultStyleSheets::defaultStyle, "defaultStyle");
     info.addMember(CSSDefaultStyleSheets::defaultQuirksStyle, "defaultQuirksStyle");
     info.addMember(CSSDefaultStyleSheets::defaultPrintStyle, "defaultPrintStyle");
     info.addMember(CSSDefaultStyleSheets::defaultViewSourceStyle, "defaultViewSourceStyle");
 }
 
 } // namespace WebCore