Implement platform deleters per spec.

Source/bindings/tests/results/V8TestEventTarget.cpp

Index: Source/bindings/tests/results/V8TestEventTarget.cpp
diff --git a/Source/bindings/tests/results/V8TestEventTarget.cpp b/Source/bindings/tests/results/V8TestEventTarget.cpp
index 315c861ef91db82d8a53160430a55a070f185d77..49011fd15b906547b8c7f5db901865cd41bc8396 100644
--- a/Source/bindings/tests/results/V8TestEventTarget.cpp
+++ b/Source/bindings/tests/results/V8TestEventTarget.cpp
@@ -215,8 +215,10 @@ static void namedPropertyDeleter(v8::Local<v8::String> name, const v8::PropertyC
 {
     TestEventTarget* collection = V8TestEventTarget::toNative(info.Holder());
     AtomicString propertyName = toCoreAtomicString(name);
-    bool result = collection->anonymousNamedDeleter(propertyName);
-    return v8SetReturnValueBool(info, result);
+    bool result = true;
+    bool knownProperty = collection->anonymousNamedDeleter(propertyName, result);
+    if (knownProperty)
+        return v8SetReturnValueBool(info, result);
 }
 
 static void namedPropertyDeleterCallback(v8::Local<v8::String> name, const v8::PropertyCallbackInfo<v8::Boolean>& info)