More FWL interface cleanup.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 747c6305bd5329d446666e7dcd06dbc9361f0f8b..bb78503537bb96dd75e37f60738cb4c45b3070b6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1030,10 +1030,6 @@ if (pdf_enable_xfa) {
       "xfa/fwl/core/fwl_noteimp.h",
       "xfa/fwl/core/fwl_sdadapterimp.cpp",
       "xfa/fwl/core/fwl_sdadapterimp.h",
-      "xfa/fwl/core/fwl_targetimp.cpp",
-      "xfa/fwl/core/fwl_targetimp.h",
-      "xfa/fwl/core/fwl_threadimp.cpp",
-      "xfa/fwl/core/fwl_threadimp.h",
       "xfa/fwl/core/fwl_timerimp.cpp",
       "xfa/fwl/core/fwl_widgetdef.h",
       "xfa/fwl/core/fwl_widgetimp.cpp",
@@ -1046,17 +1042,12 @@ if (pdf_enable_xfa) {
       "xfa/fwl/core/ifwl_app.h",
       "xfa/fwl/core/ifwl_dataprovider.h",
       "xfa/fwl/core/ifwl_form.h",
-      "xfa/fwl/core/ifwl_notedriver.h",
-      "xfa/fwl/core/ifwl_noteloop.h",
-      "xfa/fwl/core/ifwl_target.h",
       "xfa/fwl/core/ifwl_themeprovider.h",
-      "xfa/fwl/core/ifwl_thread.h",
       "xfa/fwl/core/ifwl_timer.h",
       "xfa/fwl/core/ifwl_tooltiptarget.h",
       "xfa/fwl/core/ifwl_widget.h",
       "xfa/fwl/core/ifwl_widgetdelegate.h",
       "xfa/fwl/core/ifwl_widgetmgr.h",
-      "xfa/fwl/core/ifwl_widgetmgrdelegate.h",
       "xfa/fwl/core/include/ifwl_adaptertimermgr.h",
       "xfa/fwl/lightwidget/cfwl_barcode.cpp",
       "xfa/fwl/lightwidget/cfwl_barcode.h",