Clean up singleton implementation

BUILD.gn

 # Copyright 2016 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")
 import("pdfium.gni")
 
 config("pdfium_common_config") {
   cflags = []
@@ skipping 782 matching lines @@
       "fpdfsdk/javascript/Document.h",
       "fpdfsdk/javascript/Field.cpp",
       "fpdfsdk/javascript/Field.h",
       "fpdfsdk/javascript/Icon.cpp",
       "fpdfsdk/javascript/Icon.h",
       "fpdfsdk/javascript/JS_Define.h",
       "fpdfsdk/javascript/JS_EventHandler.cpp",
       "fpdfsdk/javascript/JS_EventHandler.h",
       "fpdfsdk/javascript/JS_GlobalData.cpp",
       "fpdfsdk/javascript/JS_GlobalData.h",
+      "fpdfsdk/javascript/JS_KeyValue.cpp",
+      "fpdfsdk/javascript/JS_KeyValue.h",
       "fpdfsdk/javascript/JS_Object.cpp",
       "fpdfsdk/javascript/JS_Object.h",
       "fpdfsdk/javascript/JS_Value.cpp",
       "fpdfsdk/javascript/JS_Value.h",
       "fpdfsdk/javascript/PublicMethods.cpp",
       "fpdfsdk/javascript/PublicMethods.h",
       "fpdfsdk/javascript/app.cpp",
       "fpdfsdk/javascript/app.h",
       "fpdfsdk/javascript/cjs_context.cpp",
       "fpdfsdk/javascript/cjs_context.h",
@@ skipping 275 matching lines @@
       "xfa/fwl/lightwidget/cfwl_listbox.cpp",
       "xfa/fwl/lightwidget/cfwl_listbox.h",
       "xfa/fwl/lightwidget/cfwl_picturebox.cpp",
       "xfa/fwl/lightwidget/cfwl_picturebox.h",
       "xfa/fwl/lightwidget/cfwl_pushbutton.cpp",
       "xfa/fwl/lightwidget/cfwl_pushbutton.h",
       "xfa/fwl/lightwidget/cfwl_widget.cpp",
       "xfa/fwl/lightwidget/cfwl_widget.h",
       "xfa/fwl/lightwidget/cfwl_widgetproperties.cpp",
       "xfa/fwl/lightwidget/cfwl_widgetproperties.h",
+      "xfa/fwl/theme/cfwl_arrowdata.cpp",
+      "xfa/fwl/theme/cfwl_arrowdata.h",
       "xfa/fwl/theme/cfwl_barcodetp.cpp",
       "xfa/fwl/theme/cfwl_barcodetp.h",
       "xfa/fwl/theme/cfwl_carettp.cpp",
       "xfa/fwl/theme/cfwl_carettp.h",
       "xfa/fwl/theme/cfwl_checkboxtp.cpp",
       "xfa/fwl/theme/cfwl_checkboxtp.h",
       "xfa/fwl/theme/cfwl_comboboxtp.cpp",
       "xfa/fwl/theme/cfwl_comboboxtp.h",
       "xfa/fwl/theme/cfwl_datetimepickedtp.cpp",
       "xfa/fwl/theme/cfwl_datetimepickertp.h",
@@ skipping 476 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }