Remove last CJX_ classes that do not meaningfully extend superclasses

Add a comment to cjx_object.h to describe new situation.

Change-Id: I8e5ae815d3f9cad8b022e83dc491a8c0ce07a62a
Reviewed-on: https://pdfium-review.googlesource.com/c/48950
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

xfa/fxfa/parser/cxfa_deltas.cpp

diff --git a/xfa/fxfa/parser/cxfa_deltas.cpp b/xfa/fxfa/parser/cxfa_deltas.cpp
index 4db0936..c55595c 100644
--- a/xfa/fxfa/parser/cxfa_deltas.cpp
+++ b/xfa/fxfa/parser/cxfa_deltas.cpp
@@ -6,10 +6,10 @@
 
 #include "xfa/fxfa/parser/cxfa_deltas.h"
 
-#include "fxjs/xfa/cjx_deltas.h"
+#include "fxjs/xfa/cjx_list.h"
 #include "third_party/base/ptr_util.h"
 
 CXFA_Deltas::CXFA_Deltas(CXFA_Document* doc)
-    : CXFA_List(doc, pdfium::MakeUnique<CJX_Deltas>(this)) {}
+    : CXFA_List(doc, pdfium::MakeUnique<CJX_List>(this)) {}
 
 CXFA_Deltas::~CXFA_Deltas() {}

xfa/fxfa/parser/cxfa_sourceset.cpp

diff --git a/xfa/fxfa/parser/cxfa_sourceset.cpp b/xfa/fxfa/parser/cxfa_sourceset.cpp
index a968e4e..91be852 100644
--- a/xfa/fxfa/parser/cxfa_sourceset.cpp
+++ b/xfa/fxfa/parser/cxfa_sourceset.cpp
@@ -6,7 +6,7 @@
 
 #include "xfa/fxfa/parser/cxfa_sourceset.h"
 
-#include "fxjs/xfa/cjx_sourceset.h"
+#include "fxjs/xfa/cjx_model.h"
 #include "third_party/base/ptr_util.h"
 
 namespace {
@@ -28,6 +28,6 @@
                 XFA_Element::SourceSet,
                 nullptr,
                 kSourceSetAttributeData,
-                pdfium::MakeUnique<CJX_SourceSet>(this)) {}
+                pdfium::MakeUnique<CJX_Model>(this)) {}
 
 CXFA_SourceSet::~CXFA_SourceSet() = default;

xfa/fxfa/parser/xfa_basic_data.cpp

diff --git a/xfa/fxfa/parser/xfa_basic_data.cpp b/xfa/fxfa/parser/xfa_basic_data.cpp
index e9dd9d4..5976d73 100644
--- a/xfa/fxfa/parser/xfa_basic_data.cpp
+++ b/xfa/fxfa/parser/xfa_basic_data.cpp
@@ -34,6 +34,7 @@
 #include "fxjs/xfa/cjx_layoutpseudomodel.h"
 #include "fxjs/xfa/cjx_logpseudomodel.h"
 #include "fxjs/xfa/cjx_manifest.h"
+#include "fxjs/xfa/cjx_model.h"
 #include "fxjs/xfa/cjx_node.h"
 #include "fxjs/xfa/cjx_occur.h"
 #include "fxjs/xfa/cjx_packet.h"
@@ -41,7 +42,6 @@
 #include "fxjs/xfa/cjx_script.h"
 #include "fxjs/xfa/cjx_signaturepseudomodel.h"
 #include "fxjs/xfa/cjx_source.h"
-#include "fxjs/xfa/cjx_sourceset.h"
 #include "fxjs/xfa/cjx_subform.h"
 #include "fxjs/xfa/cjx_subformset.h"
 #include "fxjs/xfa/cjx_text.h"