Merge delegates into IFWL_* classes.

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 1186 matching lines @@
       "xfa/fwl/core/ifwl_app.cpp",
       "xfa/fwl/core/ifwl_app.h",
       "xfa/fwl/core/ifwl_barcode.cpp",
       "xfa/fwl/core/ifwl_barcode.h",
       "xfa/fwl/core/ifwl_caret.cpp",
       "xfa/fwl/core/ifwl_caret.h",
       "xfa/fwl/core/ifwl_checkbox.cpp",
       "xfa/fwl/core/ifwl_checkbox.h",
       "xfa/fwl/core/ifwl_combobox.cpp",
       "xfa/fwl/core/ifwl_combobox.h",
+      "xfa/fwl/core/ifwl_comboboxproxy.cpp",
+      "xfa/fwl/core/ifwl_comboboxproxy.h",
       "xfa/fwl/core/ifwl_comboedit.cpp",
       "xfa/fwl/core/ifwl_comboedit.h",
       "xfa/fwl/core/ifwl_combolist.cpp",
       "xfa/fwl/core/ifwl_combolist.h",
       "xfa/fwl/core/ifwl_dataprovider.h",
       "xfa/fwl/core/ifwl_datetimecalendar.cpp",
       "xfa/fwl/core/ifwl_datetimecalendar.h",
       "xfa/fwl/core/ifwl_datetimeedit.cpp",
       "xfa/fwl/core/ifwl_datetimeedit.h",
       "xfa/fwl/core/ifwl_datetimepicker.cpp",
@@ skipping 538 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }