Fix EditingStyle::mergeStyle()'s handling of custom properties

third_party/WebKit/Source/core/css/StylePropertySet.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Research In Motion Limited. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * 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 272 matching lines @@
 bool StylePropertySet::isPropertyImplicit(CSSPropertyID propertyID) const
 {
     int foundPropertyIndex = findPropertyIndex(propertyID);
     if (foundPropertyIndex == -1)
         return false;
     return propertyAt(foundPropertyIndex).isImplicit();
 }
 
 bool MutableStylePropertySet::setProperty(CSSPropertyID unresolvedProperty, const String& value, bool important, StyleSheetContents* contextStyleSheet)
 {
+    DCHECK_GE(unresolvedProperty, firstCSSProperty);
+
     // Setting the value to an empty string just removes the property in both IE and Gecko.
     // Setting it to null seems to produce less consistent results, but we treat it just the same.
     if (value.isEmpty())
         return removeProperty(resolveCSSPropertyID(unresolvedProperty));
 
     // When replacing an existing property value, this moves the property to the end of the list.
     // Firefox preserves the position, and MSIE moves the property to the beginning.
     return CSSParser::parseValue(this, unresolvedProperty, value, important, contextStyleSheet);
 }
 
@@ skipping 265 matching lines @@
 {
     return new MutableStylePropertySet(cssParserMode);
 }
 
 MutableStylePropertySet* MutableStylePropertySet::create(const CSSProperty* properties, unsigned count)
 {
     return new MutableStylePropertySet(properties, count);
 }
 
 } // namespace blink