[bindings] Implment postMessageImpl and replace the usage of postMessageMethodCommon.

Source/bindings/templates/interface_base.cpp

 {% include 'copyright_block.txt' %}
 #include "config.h"
 {% filter conditional(conditional_string) %}
 #include "{{v8_class_or_partial}}.h"
 
 {% for filename in cpp_includes if filename != '%s.h' % cpp_class_or_partial %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
@@ skipping 119 matching lines @@
     {{cpp_class}}* impl = {{v8_class}}::toImpl(host);
     return BindingSecurity::shouldAllowAccessToFrame(v8::Isolate::GetCurrent(), impl->frame(), DoNotReportSecurityError);
 }
 
 {% endif %}
 {% endblock %}
 {##############################################################################}
 {# Methods #}
 {% from 'methods.cpp' import generate_method, overload_resolution_method,
        method_callback, origin_safe_method_getter, generate_constructor,
-       method_implemented_in_private_script, runtime_determined_length_method,
-       runtime_determined_maxarg_method
+       method_implemented_in_private_script, generate_post_message_impl,
+       runtime_determined_length_method, runtime_determined_maxarg_method
        with context %}
 {% for method in methods %}
 {% if method.should_be_exposed_to_script %}
 {% for world_suffix in method.world_suffixes %}
 {% if not method.is_custom and not method.is_post_message and method.visible %}
 {{generate_method(method, world_suffix)}}
 {% endif %}
+{% if method.is_post_message %}
+{{generate_post_message_impl()}}
+{% endif %}
 {% if method.overloads and method.overloads.visible %}
 {% if method.overloads.runtime_determined_lengths %}
 {{runtime_determined_length_method(method.overloads)}}
 {% endif %}
 {% if method.overloads.runtime_determined_maxargs %}
 {{runtime_determined_maxarg_method(method.overloads)}}
 {% endif %}
 {{overload_resolution_method(method.overloads, world_suffix)}}
 {% endif %}
 {% if not method.overload_index or method.overloads %}
@@ skipping 332 matching lines @@
 {% endfor %}
 {% for attribute in attributes if attribute.is_implemented_in_private_script %}
 {{attribute_getter_implemented_in_private_script(attribute)}}
 {% if attribute.has_setter %}
 {{attribute_setter_implemented_in_private_script(attribute)}}
 {% endif %}
 {% endfor %}
 {% block partial_interface %}{% endblock %}
 } // namespace blink
 {% endfilter %}