Split the common event classes out to files.

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 1160 matching lines @@
       "xfa/fwl/core/cfwl_barcode.cpp",
       "xfa/fwl/core/cfwl_barcode.h",
       "xfa/fwl/core/cfwl_checkbox.cpp",
       "xfa/fwl/core/cfwl_checkbox.h",
       "xfa/fwl/core/cfwl_combobox.cpp",
       "xfa/fwl/core/cfwl_combobox.h",
       "xfa/fwl/core/cfwl_datetimepicker.cpp",
       "xfa/fwl/core/cfwl_datetimepicker.h",
       "xfa/fwl/core/cfwl_edit.cpp",
       "xfa/fwl/core/cfwl_edit.h",
+      "xfa/fwl/core/cfwl_event.cpp",
       "xfa/fwl/core/cfwl_event.h",
+      "xfa/fwl/core/cfwl_evtclick.cpp",
+      "xfa/fwl/core/cfwl_evtclick.h",
+      "xfa/fwl/core/cfwl_evtclose.cpp",
+      "xfa/fwl/core/cfwl_evtclose.h",
+      "xfa/fwl/core/cfwl_evtkey.cpp",
+      "xfa/fwl/core/cfwl_evtkey.h",
+      "xfa/fwl/core/cfwl_evtkillfocus.cpp",
+      "xfa/fwl/core/cfwl_evtkillfocus.h",
+      "xfa/fwl/core/cfwl_evtmouse.cpp",
+      "xfa/fwl/core/cfwl_evtmouse.h",
+      "xfa/fwl/core/cfwl_evtmousewheel.cpp",
+      "xfa/fwl/core/cfwl_evtmousewheel.h",
+      "xfa/fwl/core/cfwl_evtscroll.cpp",
+      "xfa/fwl/core/cfwl_evtscroll.h",
+      "xfa/fwl/core/cfwl_evtsetfocus.cpp",
+      "xfa/fwl/core/cfwl_evtsetfocus.h",
+      "xfa/fwl/core/cfwl_evtsizechanged.cpp",
+      "xfa/fwl/core/cfwl_evtsizechanged.h",
       "xfa/fwl/core/cfwl_listbox.cpp",
       "xfa/fwl/core/cfwl_listbox.h",
       "xfa/fwl/core/cfwl_listitem.cpp",
       "xfa/fwl/core/cfwl_listitem.h",
       "xfa/fwl/core/cfwl_message.cpp",
       "xfa/fwl/core/cfwl_message.h",
       "xfa/fwl/core/cfwl_msgkey.cpp",
       "xfa/fwl/core/cfwl_msgkey.h",
       "xfa/fwl/core/cfwl_msgkillfocus.cpp",
       "xfa/fwl/core/cfwl_msgkillfocus.h",
@@ skipping 593 matching lines @@
       "//samples",
     ]
   }
   group("fuzzers") {
     testonly = true
     deps = [
       "//testing/libfuzzer",
     ]
   }
 }