Make default for deep parameter in importNode false

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 9493a48f3fc54d1e4a102160a3adc8cee8ccfd34..8e9cdf0f81709bf8d8ed945d02d9b720f1825228 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -727,6 +727,10 @@ String UseCounter::deprecationMessage(Feature feature)
     case RangeDetach:
         return "'Range.detach' is now a no-op, as per DOM (http://dom.spec.whatwg.org/#dom-range-detach).";
 
+    case DocumentImportNodeOptionalArgument:
+        return "The behavior of importNode() with no boolean argument is about to change from doing a deep clone to doing a shallow clone.  "
+            "Make sure to pass an explicit boolean argument to keep your current behavior.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();