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

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/testing/CallbackFunctionTest.h"
 
 #include "bindings/core/v8/TestCallback.h"
 #include "bindings/core/v8/TestInterfaceCallback.h"
 #include "bindings/core/v8/TestReceiverObjectCallback.h"
 #include "bindings/core/v8/TestSequenceCallback.h"
@@ skipping 11 matching lines @@
   ScriptWrappable* scriptWrappable;
   String returnValue;
 
   if (callback->call(scriptWrappable = nullptr, message1, message2,
                      returnValue)) {
     return String("SUCCESS: ") + returnValue;
   }
   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,
     ExceptionState& exceptionState) {
   ScriptWrappable* scriptWrappable;
 
   callback->call(scriptWrappable = nullptr, divElement);
   return;
 }
 
 void CallbackFunctionTest::testReceiverObjectCallback(
     TestReceiverObjectCallback* callback,
     ExceptionState& exceptionState) {
   callback->call(this);
   return;
 }
 
 Vector<String> CallbackFunctionTest::testSequenceCallback(
     TestSequenceCallback* callback,
     const Vector<int>& numbers,
     ExceptionState& exceptionState) {
   Vector<String> returnValue;
   if (callback->call(nullptr, numbers, returnValue)) {
     return returnValue;
   }
   return Vector<String>();
 }
 
 }  // namespace blink