Add deprecation message for -webkit-background-composite

third_party/WebKit/Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 973 matching lines @@
     //
     // Be considerate to developers' consoles: features should only send
     // deprecation warnings when we're actively interested in removing them from
     // the platform.
     //
     // For shared workers and service workers, the ExecutionContext* overload
     // doesn't count the usage but only sends a console warning.
     static void countDeprecation(const LocalFrame*, Feature);
     static void countDeprecation(ExecutionContext*, Feature);
     static void countDeprecation(const Document&, Feature);
+
+    static void showDeprecationWarning(const LocalFrame*, CSSPropertyID);
     // Use countDeprecationIfNotPrivateScript() instead of countDeprecation()
     // if you don't want to count metrics in private scripts. You should use
     // countDeprecationIfNotPrivateScript() in a binding layer.
     static void countDeprecationIfNotPrivateScript(v8::Isolate*, ExecutionContext*, Feature);
     static String deprecationMessage(Feature);
 
+    // CSSPropertyIDs that aren't deprecated don't have a deprecation message.

[alancutter (OOO until 2018), 2016/01/20 00:58:27]

// CSSPropertyIDs that aren't deprecated return an empty string.

+    static String deprecationMessage(CSSPropertyID);
+
     // Return whether the Feature was previously counted for this document.
     // NOTE: only for use in testing.
     static bool isCounted(Document&, Feature);
 
     void didCommitLoad();
 
     static UseCounter* getFrom(const Document*);
     static UseCounter* getFrom(const CSSStyleSheet*);
     static UseCounter* getFrom(const StyleSheetContents*);
 
@@ skipping 42 matching lines @@
 
     bool hasRecordedMeasurement(Feature feature) const { return m_countBits.hasRecordedMeasurement(feature); }
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h