Add assert that only one of initial or inherit applyValueCSSPropertyVariable()

third_party/WebKit/Source/core/css/resolver/StyleBuilderCustom.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  * 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.
@@ skipping 909 matching lines @@
       else
         state.style()->setResolvedNonInheritedVariable(
             name, declaration.value(), parsedValue);
       return;
     }
     if (isInheritedProperty)
       inherit = true;
     else
       initial = true;
   }
+  DCHECK(initial ^ inherit);
 
   state.style()->removeVariable(name, isInheritedProperty);
   if (initial) {
     return;
   }
 
   DCHECK(inherit);
   CSSVariableData* parentValue =
       state.parentStyle()->getVariable(name, isInheritedProperty);
   const CSSValue* parentCSSValue =
@@ skipping 88 matching lines @@
     state.style()->setCaretColor(
         StyleBuilderConverter::convertStyleAutoColor(state, value));
   }
   if (state.applyPropertyToVisitedLinkStyle()) {
     state.style()->setVisitedLinkCaretColor(
         StyleBuilderConverter::convertStyleAutoColor(state, value, true));
   }
 }
 
 }  // namespace blink