WIP bindings: Add support for the record<K,V> WebIDL type.

third_party/WebKit/Source/bindings/templates/callback_function.cpp.tmpl

 {% from 'utilities.cpp.tmpl' import v8_value_to_local_cpp_value %}
 {% filter format_blink_cpp_source_code %}
 
 {% include 'copyright_block.txt' %}
 
 #include "{{cpp_class}}.h"
 
 {% for filename in cpp_includes %}
 #include "{{filename}}"
 {% endfor %}
@@ skipping 56 matching lines @@
   if (V8ScriptRunner::callFunction(m_callback.newLocal(m_scriptState->isolate()), m_scriptState->getExecutionContext(), thisValue, {{arguments | length}}, argv, m_scriptState->isolate()).ToLocal(&v8ReturnValue)) {
     {% if return_value %}
     {{v8_value_to_local_cpp_value(return_value) | indent(8)}}
     returnValue = cppValue;
     {% endif %}
     return true;
   }
   return false;
 }
 
+{{cpp_class}}* NativeValueTraits<{{cpp_class}}>::nativeValue(v8::Isolate* isolate, v8::Local<v8::Value> value, ExceptionState& exceptionState) {
+  return {{cpp_class}}::create(ScriptState::current(isolate), value);
+}
+
 }  // namespace blink
 
 {% endfilter %}{# format_blink_cpp_source_code #}