Add deprecation message for -webkit-background-composite

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

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2012 Apple Inc. 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 54 matching lines @@
     , m_isMutable(false)
     , m_isInMemoryCache(false)
     , m_hasFontFaceRule(false)
     , m_hasMediaQueries(false)
     , m_hasSingleOwnerDocument(true)
     , m_parserContext(context)
 {
 }
 
 StyleSheetContents::StyleSheetContents(const StyleSheetContents& o)
-    : m_ownerRule(nullptr)
+    : m_ownerRule(o.m_ownerRule)

[Timothy Loh, 2016/01/25 00:40:00]

why was this originally nullptr?

[nainar, 2016/01/25 03:48:24]

I wasn't able to track the down the reason using Git Blame.

The reason I added this here was that singleOwnerDocument() used m_ownerRule and
in case this constructor was called it would be missing a value for m_ownerRule.

     , m_originalURL(o.m_originalURL)
     , m_importRules(o.m_importRules.size())
     , m_namespaceRules(o.m_namespaceRules.size())
     , m_childRules(o.m_childRules.size())
     , m_namespaces(o.m_namespaces)
     , m_defaultNamespace(o.m_defaultNamespace)
     , m_hasSyntacticallyValidCSSHeader(o.m_hasSyntacticallyValidCSSHeader)
     , m_didLoadErrorOccur(false)
     , m_isMutable(false)
     , m_isInMemoryCache(false)
@@ skipping 589 matching lines @@
     visitor->trace(m_importRules);
     visitor->trace(m_namespaceRules);
     visitor->trace(m_childRules);
     visitor->trace(m_loadingClients);
     visitor->trace(m_completedClients);
     visitor->trace(m_ruleSet);
 #endif
 }
 
 }