Fix stack overflow in object Clone() functions

core/fpdfapi/fpdf_parser/cpdf_dictionary.cpp

Index: core/fpdfapi/fpdf_parser/cpdf_dictionary.cpp
diff --git a/core/fpdfapi/fpdf_parser/cpdf_dictionary.cpp b/core/fpdfapi/fpdf_parser/cpdf_dictionary.cpp
index 78b88a1b2f1a84027057b72047a41b871f4fd162..8fef074d4bd184ded1d831f406f4ec470b85cbf1 100644
--- a/core/fpdfapi/fpdf_parser/cpdf_dictionary.cpp
+++ b/core/fpdfapi/fpdf_parser/cpdf_dictionary.cpp
@@ -18,6 +18,7 @@
 CPDF_Dictionary::CPDF_Dictionary() {}
 
 CPDF_Dictionary::~CPDF_Dictionary() {
+  m_ObjNum = kInvalidObjNum;
   for (const auto& it : m_Map)
     it.second->Release();
 }
@@ -44,10 +45,22 @@ const CPDF_Dictionary* CPDF_Dictionary::AsDictionary() const {
   return this;
 }
 
-CPDF_Object* CPDF_Dictionary::Clone(FX_BOOL bDirect) const {
+CPDF_Object* CPDF_Dictionary::Clone() const {
+  return CloneObjectNonCyclic(false);
+}
+
+CPDF_Object* CPDF_Dictionary::CloneNonCyclic(
+    bool bDirect,
+    std::set<const CPDF_Object*>* pVisited) const {
+  pVisited->insert(this);
   CPDF_Dictionary* pCopy = new CPDF_Dictionary();
-  for (const auto& it : *this)
-    pCopy->m_Map.insert(std::make_pair(it.first, it.second->Clone(bDirect)));
+  for (const auto& it : *this) {
+    CPDF_Object* value = it.second;
+    if (!pdfium::ContainsKey(*pVisited, value)) {
+      pCopy->m_Map.insert(
+          std::make_pair(it.first, value->CloneNonCyclic(bDirect, pVisited)));
+    }
+  }
   return pCopy;
 }