Revert of Introduce InterfaceEndpointClient(IEC), InterfaceEndpointHandle and

mojo/public/tools/bindings/generators/js_templates/interface_definition.tmpl

 {%- for method in interface.methods %}
   var k{{interface.name}}_{{method.name}}_Name = {{method.ordinal}};
 {%- endfor %}
 
   function {{interface.name}}Ptr(handleOrPtrInfo) {
     this.ptr = new bindings.InterfacePtrController({{interface.name}},
                                                    handleOrPtrInfo);
   }
 
   function {{interface.name}}Proxy(receiver) {
@@ skipping 75 matching lines @@
   };
 
   {{interface.name}}Stub.prototype.acceptWithResponder =
       function(message, responder) {
     var reader = new codec.MessageReader(message);
     switch (reader.messageName) {
 {%- for method in interface.methods %}
 {%- if method.response_parameters != None %}
     case k{{interface.name}}_{{method.name}}_Name:
       var params = reader.decodeStruct({{interface.name}}_{{method.name}}_Params);
-      this.{{method.name|stylize_method}}(
+      return this.{{method.name|stylize_method}}(
 {%- for parameter in method.parameters -%}
 params.{{parameter.name}}{% if not loop.last %}, {% endif -%}
 {%- endfor %}).then(function(response) {
         var responseParams =
             new {{interface.name}}_{{method.name}}_ResponseParams();
 {%-     for parameter in method.response_parameters %}
         responseParams.{{parameter.name}} = response.{{parameter.name}};
 {%-     endfor %}
         var builder = new codec.MessageWithRequestIDBuilder(
             k{{interface.name}}_{{method.name}}_Name,
             codec.align({{interface.name}}_{{method.name}}_ResponseParams.encodedSize),
             codec.kMessageIsResponse, reader.requestID);
         builder.encodeStruct({{interface.name}}_{{method.name}}_ResponseParams,
                              responseParams);
         var message = builder.finish();
         responder.accept(message);
       });
-      return true;
 {%- endif %}
 {%- endfor %}
     default:
-      return false;
+      return Promise.reject(Error("Unhandled message: " + reader.messageName));
     }
   };
 
 {#--- Validation #}
 
   function validate{{interface.name}}Request(messageValidator) {
 {%- if not(interface.methods) %}
     return validator.validationError.NONE;
 {%- else %}
     var message = messageValidator.message;
@@ skipping 60 matching lines @@
 {%- from "enum_definition.tmpl" import enum_def -%}
 {%- for enum in interface.enums %}
   {{ enum_def("%s.%s"|format(interface.name, enum.name), enum) }}
 {%-  endfor %}
   {{interface.name}}Stub.prototype.validator = validate{{interface.name}}Request;
 {%- if interface|has_callbacks %}
   {{interface.name}}Proxy.prototype.validator = validate{{interface.name}}Response;
 {%- else %}
   {{interface.name}}Proxy.prototype.validator = null;
 {%- endif %}