Add Ignition to about:flags.

gin/gin.gyp

 # Copyright 2013 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.
 
 {
   'variables': {
     'chromium_code': 1,
     'gin_gen_path': '<(SHARED_INTERMEDIATE_DIR)/gin/',
   },
   'targets': [
@@ skipping 20 matching lines @@
         '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_platform.h',
         'public/wrapper_info.h',
         'runner.cc',
         'runner.h',
         'run_microtasks_observer.cc',
         'run_microtasks_observer.h',
         'shell_runner.cc',
         'shell_runner.h',
         'try_catch.cc',
@@ skipping 112 matching lines @@
             '../build/isolate.gypi',
           ],
           'sources': [
             'gin_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }