Update union conversion algorithm

third_party/WebKit/Source/core/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/config/chrome_build.gni")
 import("//build/config/ui.gni")
 import("//third_party/WebKit/Source/bindings/bindings.gni")
 import("//third_party/WebKit/Source/bindings/core/v8/generated.gni")
 import("//third_party/WebKit/Source/bindings/modules/modules.gni")
 import("//third_party/WebKit/Source/bindings/modules/v8/generated.gni")
@@ skipping 272 matching lines @@
   configs += [
     "//third_party/WebKit/Source:inside_blink",
     "//third_party/WebKit/Source:config",
   ]
 
   deps = [
     ":core",
     ":generated_testing_idls",
   ]
 
-  sources = generated_core_testing_dictionary_files + webcore_testing_files
+  sources =
+      generated_core_testing_dictionary_files +
+      bindings_core_generated_testing_union_type_files + webcore_testing_files
   sources += [
     "$bindings_core_v8_output_dir/V8DictionaryTest.cpp",
     "$bindings_core_v8_output_dir/V8DictionaryTest.h",
     "$bindings_core_v8_output_dir/V8GCObservation.cpp",
     "$bindings_core_v8_output_dir/V8GCObservation.h",
     "$bindings_core_v8_output_dir/V8GarbageCollectedScriptWrappable.cpp",
     "$bindings_core_v8_output_dir/V8GarbageCollectedScriptWrappable.h",
     "$bindings_core_v8_output_dir/V8InternalDictionary.cpp",
     "$bindings_core_v8_output_dir/V8InternalDictionary.h",
     "$bindings_core_v8_output_dir/V8InternalDictionaryDerived.cpp",
@@ skipping 716 matching lines @@
     "$blink_core_output_dir/{{source_name_part}}.h",
   ]
   args = [
     "{{source}}",
     rel_blink_core_gen_dir,
     bison_exe,
   ]
 
   deps = make_core_generated_deps
 }