Cpp bindings: Return false from Validator::Accept() on unrecognized message or invalid flags

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

Index: mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
index 308c8b67a5060845834470782594e599e915e6a6..292b0ae2b71f97d7bbc54e98fd3d996b35b12de8 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/interface_definition.tmpl
@@ -243,6 +243,11 @@ bool {{class_name}}RequestValidator::Accept(mojo::Message* message) {
       break;
     }
 {%-   endfor %}
+    default: {
+      // Unrecognized message.
+      ReportValidationError(mojo::internal::VALIDATION_ERROR_UNKOWN_METHOD);
+      return false;
+    }
   }
 {%- endif %}
 
@@ -273,6 +278,11 @@ bool {{class_name}}ResponseValidator::Accept(mojo::Message* message) {
       break;
     }
 {%-   endfor %}
+    default: {
+      // Unrecognized message.
+      ReportValidationError(mojo::internal::VALIDATION_ERROR_UNKOWN_METHOD);
+      return false;
+    }
   }
 {%- endif %}