Add inheritance support to Webmodules template.

third_party/WebKit/Source/bindings/templates/web_module_interface.h.tmpl

 {% filter format_blink_cpp_source_code %}
 
 {% include 'copyright_block.txt' %}
 
 // TODO(dglazkov): Use chromium-style path.
 #ifndef {{class_name}}_h
 #define {{class_name}}_h
 
 {% for include_file in header_includes %}
 #include "{{include_file}}"
 {% endfor %}
 
 namespace blink {
 namespace api {
 
-class {{class_name}} {
+class {{class_name}}{{inherits_expression}} {
 
 };
 
 }  // namespace api
 }  // namespace blink
 
 #endif  // {{class_name}}_h
 
 {% endfilter %}