IDL: Union type support for attributes

Source/bindings/templates/union.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 "{{header_filename}}"
 
 {% macro assign_and_return_if_hasinstance(member) %}
 if (V8{{member.type_name}}::hasInstance(v8Value, isolate)) {
     {{member.cpp_local_type}} cppValue = V8{{member.type_name}}::toImpl(v8::Handle<v8::Object>::Cast(v8Value));
     impl.set{{member.type_name}}(cppValue);
     return;
 }
 {% endmacro %}
 {% for filename in cpp_includes %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
 
 {% for container in containers %}
 {{container.cpp_class}}::{{container.cpp_class}}()
     : m_type(SpecificTypeNone)
 {
 }
 
 {% for member in container.members %}
-{{member.rvalue_cpp_type}} {{container.cpp_class}}::getAs{{member.type_name}}()
+{{member.rvalue_cpp_type}} {{container.cpp_class}}::getAs{{member.type_name}}() const
 {
     ASSERT(is{{member.type_name}}());
     return m_{{member.cpp_name}};
 }
 
 void {{container.cpp_class}}::set{{member.type_name}}({{member.rvalue_cpp_type}} value)
 {
     ASSERT(isNull());
     m_{{member.cpp_name}} = value;
     m_type = {{member.specific_type_enum}};
@@ skipping 105 matching lines @@
     if (impl.is{{member.type_name}}())
         return {{member.cpp_value_to_v8_value}};
 
     {% endfor %}
     ASSERT_NOT_REACHED();
     return v8::Handle<v8::Value>();
 }
 
 {% endfor %}
 } // namespace blink