Create classes for XFA JS objects

This CL creates classes for the various XFA JS objects. The method
calls from xfa_basic_data_element_script have been modified to call
these methods instead of methods in CJX_Object.

Change-Id: Idb2de38656f7e8edc559d44921eba25073e6c806
Reviewed-on: https://pdfium-review.googlesource.com/21110
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
diff --git a/xfa/fxfa/parser/cxfa_keyusage.cpp b/xfa/fxfa/parser/cxfa_keyusage.cpp
index f12ab04..13054be 100644
--- a/xfa/fxfa/parser/cxfa_keyusage.cpp
+++ b/xfa/fxfa/parser/cxfa_keyusage.cpp
@@ -6,6 +6,9 @@
 
 #include "xfa/fxfa/parser/cxfa_keyusage.h"
 
+#include "fxjs/xfa/cjx_keyusage.h"
+#include "third_party/base/ptr_util.h"
+
 namespace {
 
 const CXFA_Node::AttributeData kAttributeData[] = {
@@ -37,6 +40,7 @@
                 XFA_Element::KeyUsage,
                 nullptr,
                 kAttributeData,
-                kName) {}
+                kName,
+                pdfium::MakeUnique<CJX_KeyUsage>(this)) {}
 
 CXFA_KeyUsage::~CXFA_KeyUsage() {}