bindings: Throw TypeError when required dictionary member is undefined

Source/bindings/templates/dictionary_v8.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}}. DO NOT MODIFY!
 
 #include "config.h"
 #include "{{v8_original_class}}.h"
 
 {% for filename in cpp_includes if filename != '%s.h' % v8_class %}
@@ skipping 28 matching lines @@
     v8::Local<v8::Object> v8Object = v8Value->ToObject(isolate);
     v8::TryCatch block;
     {% endif %}
     {% for member in members %}
     v8::Local<v8::Value> {{member.name}}Value = v8Object->Get(v8String(isolate, "{{member.name}}"));
     if (block.HasCaught()) {
         exceptionState.rethrowV8Exception(block.Exception());
         return;
     }
     if ({{member.name}}Value.IsEmpty() || {{member.name}}Value->IsUndefined()) {
+        {% if member.is_required %}
+        exceptionState.throwTypeError("required member {{member.name}} is undefined.");
+        return;
+        {% else %}
         // Do nothing.
+        {% endif %}
     {% if member.is_nullable %}
     } else if ({{member.name}}Value->IsNull()) {
         impl.{{member.null_setter_name}}();
     {% endif %}
     } else {
         {% if member.deprecate_as %}
         UseCounter::countDeprecationIfNotPrivateScript(isolate, callingExecutionContext(isolate), UseCounter::{{member.deprecate_as}});
         {% endif %}
         {{v8_value_to_local_cpp_value(member) | indent(8)}}
         {% if member.is_interface_type %}
@@ skipping 48 matching lines @@
 }
 
 {{cpp_class}} NativeValueTraits<{{cpp_class}}>::nativeValue(v8::Isolate* isolate, v8::Local<v8::Value> value, ExceptionState& exceptionState)
 {
     {{cpp_class}} impl;
     {{v8_class}}::toImpl(isolate, value, impl, exceptionState);
     return impl;
 }
 
 } // namespace blink