Split xfa_object_imp into individual class files.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index c9a5fdd65937b4d074eceaa21905f9794fd613c4..562036ad23cf8a4d396f1a34279722fe44e4a22d 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1328,8 +1328,10 @@ if (pdf_enable_xfa) {
       "xfa/fxfa/include/xfa_fontmgr.h",
       "xfa/fxfa/include/xfa_rendercontext.h",
       "xfa/fxfa/parser/cxfa_arc.h",
+      "xfa/fxfa/parser/cxfa_arraynodelist.cpp",
       "xfa/fxfa/parser/cxfa_assist.cpp",
       "xfa/fxfa/parser/cxfa_assist.h",
+      "xfa/fxfa/parser/cxfa_attachnodelist.cpp",
       "xfa/fxfa/parser/cxfa_bind.cpp",
       "xfa/fxfa/parser/cxfa_bind.h",
       "xfa/fxfa/parser/cxfa_binditems.cpp",
@@ -1361,6 +1363,9 @@ if (pdf_enable_xfa) {
       "xfa/fxfa/parser/cxfa_line.h",
       "xfa/fxfa/parser/cxfa_margin.cpp",
       "xfa/fxfa/parser/cxfa_margin.h",
+      "xfa/fxfa/parser/cxfa_node.cpp",
+      "xfa/fxfa/parser/cxfa_nodelist.cpp",
+      "xfa/fxfa/parser/cxfa_object.cpp",
       "xfa/fxfa/parser/cxfa_occur.cpp",
       "xfa/fxfa/parser/cxfa_occur.h",
       "xfa/fxfa/parser/cxfa_para.cpp",
@@ -1376,6 +1381,7 @@ if (pdf_enable_xfa) {
       "xfa/fxfa/parser/cxfa_submit.h",
       "xfa/fxfa/parser/cxfa_text.cpp",
       "xfa/fxfa/parser/cxfa_text.h",
+      "xfa/fxfa/parser/cxfa_thisproxy.cpp",
       "xfa/fxfa/parser/cxfa_tooltip.cpp",
       "xfa/fxfa/parser/cxfa_tooltip.h",
       "xfa/fxfa/parser/cxfa_validate.cpp",
@@ -1420,7 +1426,6 @@ if (pdf_enable_xfa) {
       "xfa/fxfa/parser/xfa_localevalue.cpp",
       "xfa/fxfa/parser/xfa_localevalue.h",
       "xfa/fxfa/parser/xfa_object.h",
-      "xfa/fxfa/parser/xfa_object_imp.cpp",
       "xfa/fxfa/parser/xfa_script.h",
       "xfa/fxfa/parser/xfa_script_datawindow.cpp",
       "xfa/fxfa/parser/xfa_script_datawindow.h",