IDL: Generate union type containers

Source/bindings/core/v8/generated.gypi

 # 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.
 
 {
   'variables': {
     'bindings_core_v8_output_dir': '<(SHARED_INTERMEDIATE_DIR)/blink/bindings/core/v8',
+    'bindings_core_v8_generated_union_type_files': [
+      '<(bindings_core_v8_output_dir)/UnionTypesCore.cpp',
+      '<(bindings_core_v8_output_dir)/UnionTypesCore.h',
+    ],
 
     'conditions': [
       ['OS=="win" and buildtype=="Official"', {
         # On Windows Official release builds, we try to preserve symbol
         # space.
         'bindings_core_v8_generated_aggregate_files': [
           '<(bindings_core_v8_output_dir)/V8GeneratedCoreBindings.cpp',
         ],
       }, {
         'bindings_core_v8_generated_aggregate_files': [
@@ skipping 14 matching lines @@
           '<(bindings_core_v8_output_dir)/V8GeneratedCoreBindings15.cpp',
           '<(bindings_core_v8_output_dir)/V8GeneratedCoreBindings16.cpp',
           '<(bindings_core_v8_output_dir)/V8GeneratedCoreBindings17.cpp',
           '<(bindings_core_v8_output_dir)/V8GeneratedCoreBindings18.cpp',
           '<(bindings_core_v8_output_dir)/V8GeneratedCoreBindings19.cpp',
         ],
       }],
     ],
   },
 }