Add Ignition to about:flags.

gin/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build_overrides/v8.gni")
 import("//testing/test.gni")
 
 component("gin") {
   sources = [
     "arguments.cc",
     "arguments.h",
     "array_buffer.cc",
     "array_buffer.h",
     "context_holder.cc",
     "converter.cc",
     "converter.h",
     "debug_impl.cc",
     "debug_impl.h",
     "dictionary.cc",
     "dictionary.h",
     "function_template.cc",
     "function_template.h",
     "gin_export.h",
+    "gin_features.cc",
     "handle.h",
     "interceptor.cc",
     "interceptor.h",
     "isolate_holder.cc",
     "modules/console.cc",
     "modules/console.h",
     "modules/file_module_provider.cc",
     "modules/file_module_provider.h",
     "modules/module_registry.cc",
     "modules/module_registry.h",
     "modules/module_registry_observer.h",
     "modules/module_runner_delegate.cc",
     "modules/module_runner_delegate.h",
     "modules/timer.cc",
     "modules/timer.h",
     "object_template_builder.cc",
     "object_template_builder.h",
     "per_context_data.cc",
     "per_context_data.h",
     "per_isolate_data.cc",
     "per_isolate_data.h",
     "public/context_holder.h",
     "public/debug.h",
     "public/gin_embedders.h",
+    "public/gin_features.h",
     "public/isolate_holder.h",
     "public/v8_idle_task_runner.h",
     "public/v8_platform.h",
     "public/wrapper_info.h",
     "run_microtasks_observer.cc",
     "run_microtasks_observer.h",
     "runner.cc",
     "runner.h",
     "shell_runner.cc",
     "shell_runner.h",
@@ skipping 137 matching lines @@
     "test/expect.js",
     "test/file_unittests.js",
     "test/gtest_unittests.js",
     "../OWNERS",
   ]
 
   data_deps = [
     ":gin_shell",
   ]
 }