Add a deprecation message for shadow-piercing descendant combinators and shadow pseudo elements.

Source/core/frame/UseCounter.cpp

 /*
  * 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 893 matching lines @@
 
     case PrefixedTouchRadiusY:
         return "'Touch.webkitRadiusY' is deprecated and will be removed in M47, around November 2015. Please use 'Touch.radiusY' instead.";
 
     case PrefixedTouchRotationAngle:
         return "'Touch.webkitRotationAngle' is deprecated and will be removed in M47, around November 2015. Please use 'Touch.rotationAngle' instead.";
 
     case PrefixedTouchForce:
         return "'Touch.webkitForce' is deprecated and will be removed in M47, around November 2015. Please use 'Touch.force' instead.";
 
+    case CSSDeepCombinator:
+        return "/deep/ combinator is deprecated. See https://www.chromestatus.com/features/6750456638341120 for more details.";
+
+    case CSSSelectorPseudoShadow:
+        return "::shadow pseudo-element is deprecated. See https://www.chromestatus.com/features/6750456638341120 for more details.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();
     }
 }
 
 void UseCounter::count(CSSParserContext context, CSSPropertyID feature)
 {
     ASSERT(feature >= firstCSSProperty);
     ASSERT(feature <= lastUnresolvedCSSProperty);
@@ skipping 27 matching lines @@
 UseCounter* UseCounter::getFrom(const StyleSheetContents* sheetContents)
 {
     // FIXME: We may want to handle stylesheets that have multiple owners
     //        http://crbug.com/242125
     if (sheetContents && sheetContents->hasSingleOwnerNode())
         return getFrom(sheetContents->singleOwnerDocument());
     return 0;
 }
 
 } // namespace blink