Revert of Remove applyAuthorStyles flag from ShadowRoot.

Source/core/frame/UseCounter.cpp

Index: Source/core/frame/UseCounter.cpp
diff --git a/Source/core/frame/UseCounter.cpp b/Source/core/frame/UseCounter.cpp
index ba5c0cca9b8a132a19a17e2afdce9f338b80fc61..af8a44487cfb35827eca4c60e41e5e7604503e2f 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -673,6 +673,9 @@
     case PrefixedPutImageDataHD:
         return "'CanvasRenderingContext2D.webkitPutImageDataHD' is deprecated. Please use putImageData instead.";
 
+    case ShadowRootApplyAuthorStyles:
+        return "'ShadowRoot.applyAuthorStyles' is deprecated.";
+
     case PrefixedSpeechAttribute:
         return "The 'x-webkit-speech' input field attribute is deprecated. Please use the JavaScript API instead.";
 
@@ -688,6 +691,7 @@
     case PrefixedCancelRequestAnimationFrame:
         return "'webkitCancelRequestAnimationFrame' is vendor-specific. Please use the standard 'cancelAnimationFrame' instead.";
 
+    // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();
     }