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

Source/bindings/templates/interface_base.cpp

Index: Source/bindings/templates/interface_base.cpp
diff --git a/Source/bindings/templates/interface_base.cpp b/Source/bindings/templates/interface_base.cpp
index 439bba7125a003e1e2c85c61a288533ef15e109a..76645ac8f370c76a8069582e211bfb64c17ebabc 100644
--- a/Source/bindings/templates/interface_base.cpp
+++ b/Source/bindings/templates/interface_base.cpp
@@ -137,8 +137,8 @@ bool namedSecurityCheck(v8::Local<v8::Object> host, v8::Local<v8::Value> key, v8
 {# 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 %}
@@ -146,6 +146,9 @@ bool namedSecurityCheck(v8::Local<v8::Object> host, v8::Local<v8::Value> key, v8
 {% 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)}}