Change IFWL_Widget to store a single delegate.

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 1380 matching lines @@
       "xfa/fxbarcode/qrcode/BC_QRCoderMaskUtil.cpp",
       "xfa/fxbarcode/qrcode/BC_QRCoderMaskUtil.h",
       "xfa/fxbarcode/qrcode/BC_QRCoderMatrixUtil.cpp",
       "xfa/fxbarcode/qrcode/BC_QRCoderMatrixUtil.h",
       "xfa/fxbarcode/qrcode/BC_QRCoderMode.cpp",
       "xfa/fxbarcode/qrcode/BC_QRCoderMode.h",
       "xfa/fxbarcode/qrcode/BC_QRCoderVersion.cpp",
       "xfa/fxbarcode/qrcode/BC_QRCoderVersion.h",
       "xfa/fxbarcode/utils.h",
       "xfa/fxfa/app/cxfa_eventparam.cpp",
+      "xfa/fxfa/app/cxfa_ffcheckbuttondelegate.cpp",
+      "xfa/fxfa/app/cxfa_ffcheckbuttondelegate.h",
+      "xfa/fxfa/app/cxfa_ffcomboboxdelegate.cpp",
+      "xfa/fxfa/app/cxfa_ffcomboboxdelegate.h",
+      "xfa/fxfa/app/cxfa_ffdatetimeeditdelegate.cpp",
+      "xfa/fxfa/app/cxfa_ffdatetimeeditdelegate.h",
+      "xfa/fxfa/app/cxfa_fffielddelegate.cpp",
+      "xfa/fxfa/app/cxfa_fffielddelegate.h",
+      "xfa/fxfa/app/cxfa_ffimageeditdelegate.cpp",
+      "xfa/fxfa/app/cxfa_ffimageeditdelegate.h",
+      "xfa/fxfa/app/cxfa_fflistboxdelegate.cpp",
+      "xfa/fxfa/app/cxfa_fflistboxdelegate.h",
+      "xfa/fxfa/app/cxfa_ffnumericeditdelegate.cpp",
+      "xfa/fxfa/app/cxfa_ffnumericeditdelegate.h",
+      "xfa/fxfa/app/cxfa_ffpushbuttondelegate.cpp",
+      "xfa/fxfa/app/cxfa_ffpushbuttondelegate.h",
+      "xfa/fxfa/app/cxfa_fftexteditdelegate.cpp",
+      "xfa/fxfa/app/cxfa_fftexteditdelegate.h",
       "xfa/fxfa/app/xfa_checksum.cpp",
       "xfa/fxfa/app/xfa_ffapp.cpp",
       "xfa/fxfa/app/xfa_ffbarcode.cpp",
       "xfa/fxfa/app/xfa_ffbarcode.h",
       "xfa/fxfa/app/xfa_ffcheckbutton.cpp",
       "xfa/fxfa/app/xfa_ffcheckbutton.h",
       "xfa/fxfa/app/xfa_ffchoicelist.cpp",
       "xfa/fxfa/app/xfa_ffchoicelist.h",
       "xfa/fxfa/app/xfa_ffdoc.cpp",
       "xfa/fxfa/app/xfa_ffdochandler.cpp",
@@ skipping 343 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }