Change IFWL_Widget to store a single delegate.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index a77ea4c6b207dc7b277420a9cc62b4a5e07e5b2a..a0f859469c7705d809e7d6b722df442f6b556382 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1398,6 +1398,24 @@ if (pdf_enable_xfa) {
       "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",