bindings: Throw a type error if converting an interface or callback function fails.

third_party/WebKit/Source/bindings/tests/results/modules/VoidCallbackFunctionModules.cpp

 // Copyright 2014 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.
 
 // This file has been auto-generated by code_generator_v8.py.
 // DO NOT MODIFY!
 
 // This file has been generated from the Jinja2 template in
 // third_party/WebKit/Source/bindings/templates/callback_function.cpp.tmpl
 
@@ skipping 61 matching lines @@
                                     0,
                                     argv,
                                     isolate).ToLocal(&v8ReturnValue)) {
     return false;
   }
 
   return true;
 }
 
 VoidCallbackFunctionModules* NativeValueTraits<VoidCallbackFunctionModules>::nativeValue(v8::Isolate* isolate, v8::Local<v8::Value> value, ExceptionState& exceptionState) {
-  return VoidCallbackFunctionModules::create(ScriptState::current(isolate), value);
+  VoidCallbackFunctionModules* nativeValue = VoidCallbackFunctionModules::create(ScriptState::current(isolate), value);
+  if (!nativeValue)
+    exceptionState.throwTypeError("Unable to convert value to VoidCallbackFunctionModules.");
+  return nativeValue;
 }
 
 }  // namespace blink