bindings: Don't throw a TypeError when 'null' is passed to nullable callback function

third_party/WebKit/Source/core/testing/CallbackFunctionTest.cpp

Index: third_party/WebKit/Source/core/testing/CallbackFunctionTest.cpp
diff --git a/third_party/WebKit/Source/core/testing/CallbackFunctionTest.cpp b/third_party/WebKit/Source/core/testing/CallbackFunctionTest.cpp
index ac5e2815802d91f95610b9c558075a2f25ef8696..0cf4339345e4dd4829284038987d8ab0513ce45b 100644
--- a/third_party/WebKit/Source/core/testing/CallbackFunctionTest.cpp
+++ b/third_party/WebKit/Source/core/testing/CallbackFunctionTest.cpp
@@ -29,6 +29,16 @@ String CallbackFunctionTest::testCallback(TestCallback* callback,
   return String("Error!");
 }
 
+String CallbackFunctionTest::testNullableCallback(
+    TestCallback* callback,
+    const String& message1,
+    const String& message2,
+    ExceptionState& exceptionState) {
+  if (!callback)
+    return String("Empty callback");
+  return testCallback(callback, message1, message2, exceptionState);
+}
+
 void CallbackFunctionTest::testInterfaceCallback(
     TestInterfaceCallback* callback,
     HTMLDivElement* divElement,