CXFA_ThisProxy is not a CXFA_Node.

Fix type-checking method IsNode() to reflect this fact.

Bug: chromium:983137
Change-Id: I40495cfdcf5a4a357bd5fa02185747b99a872412
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/57650
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

testing/resources/pixel/xfa_specific/bug_983137.in

diff --git a/testing/resources/pixel/xfa_specific/bug_983137.in b/testing/resources/pixel/xfa_specific/bug_983137.in
new file mode 100644
index 0000000..5b3b989
--- /dev/null
+++ b/testing/resources/pixel/xfa_specific/bug_983137.in
@@ -0,0 +1,51 @@
+{{header}}
+{{include ../../xfa_catalog_1_0.fragment}}
+{{include ../../xfa_object_2_0.fragment}}
+{{include ../../xfa_preamble_3_0.fragment}}
+{{include ../../xfa_config_4_0.fragment}}
+{{object 5 0}} <<
+  {{streamlen}}
+>>
+stream
+<template>
+  <subform layout="tb" name="subform1">
+    <pageSet id="page" relation="orderedOccurrence">
+      <occur initial="1" max="1" min="1"/>
+      <pageArea id="Page1" name="Page1">
+        <occur max="1" min="1"/>
+        <contentArea h="100mm" w="200mm" x="0.25in" y="0.25in"/>
+        <medium long="297mm" short="210mm" stock="a4"/>
+      </pageArea>
+    </pageSet>
+    <event activity="docReady" ref="$host">
+      <script contentType="application/x-javascript">
+      </script>
+    </event>
+    <subform layout="tb" name="subform2">
+      <variables name="vara">
+        <script contentType="application/x-javascript" name="srpt">
+          var z = xfa.record.nodes;
+          z.append(this)
+        </script>
+      </variables>
+      <occur initial="1" max="10" min="0" name="occur1">
+      </occur>
+      <field h="10mm" name="field1" w="40mm" x="10mm" y="10mm">
+        <event activity="ready" ref="$form">
+          <script contentType="application/x-javascript">
+            var b = xfa.resolveNode("vara.srpt");
+          </script>
+        </event>
+      </field>
+    </subform>
+  </subform>
+</template>
+endstream
+endobj
+{{include ../../xfa_locale_6_0.fragment}}
+{{include ../../xfa_postamble_7_0.fragment}}
+{{include ../../xfa_pages_8_0.fragment}}
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF

testing/resources/pixel/xfa_specific/bug_983137_expected.pdf.0.png

diff --git a/testing/resources/pixel/xfa_specific/bug_983137_expected.pdf.0.png b/testing/resources/pixel/xfa_specific/bug_983137_expected.pdf.0.png
new file mode 100644
index 0000000..e4e08ee
--- /dev/null
+++ b/testing/resources/pixel/xfa_specific/bug_983137_expected.pdf.0.png
Binary files differ

xfa/fxfa/parser/cxfa_object.h

diff --git a/xfa/fxfa/parser/cxfa_object.h b/xfa/fxfa/parser/cxfa_object.h
index a36531f..cfbcb13 100644
--- a/xfa/fxfa/parser/cxfa_object.h
+++ b/xfa/fxfa/parser/cxfa_object.h
@@ -55,8 +55,7 @@
            m_objectType == XFA_ObjectType::ModelNode ||
            m_objectType == XFA_ObjectType::TextNode ||
            m_objectType == XFA_ObjectType::ContainerNode ||
-           m_objectType == XFA_ObjectType::ContentNode ||
-           m_objectType == XFA_ObjectType::ThisProxy;
+           m_objectType == XFA_ObjectType::ContentNode;
   }
   bool IsTreeList() const { return m_objectType == XFA_ObjectType::TreeList; }
   bool IsContentNode() const {