diff --git a/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp b/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp
index 4e6b52f..8895b6b 100644
--- a/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_cross_ref_avail.cpp
@@ -38,7 +38,7 @@
   if (status_ == CPDF_DataAvail::DataAvailable)
     return CPDF_DataAvail::DataAvailable;
 
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   while (true) {
     bool check_result = false;
     switch (state_) {
diff --git a/core/fpdfapi/parser/cpdf_data_avail.cpp b/core/fpdfapi/parser/cpdf_data_avail.cpp
index d1513a6..1f4d1c3 100644
--- a/core/fpdfapi/parser/cpdf_data_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_data_avail.cpp
@@ -173,7 +173,7 @@
 
 bool CPDF_DataAvail::CheckAndLoadAllXref() {
   if (!m_pCrossRefAvail) {
-    const CPDF_ReadValidator::Session read_session(GetValidator());
+    CPDF_ReadValidator::ScopedSession read_session(GetValidator());
     const FX_FILESIZE last_xref_offset = m_parser.ParseStartXRef();
     if (GetValidator()->has_read_problems())
       return false;
@@ -221,7 +221,7 @@
 
   RetainPtr<CPDF_Object> pRet;
   if (pParser) {
-    const CPDF_ReadValidator::Session read_session(GetValidator());
+    CPDF_ReadValidator::ScopedSession read_session(GetValidator());
     pRet = pParser->ParseIndirectObject(objnum);
     if (GetValidator()->has_read_problems())
       return nullptr;
@@ -240,7 +240,7 @@
     return true;
   }
 
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   m_parser.ParseIndirectObject(dwInfoObjNum);
   if (GetValidator()->has_read_problems())
     return false;
@@ -256,7 +256,7 @@
     return true;
   }
 
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   m_pRoot = ToDictionary(m_parser.ParseIndirectObject(dwRootObjNum));
   if (GetValidator()->has_read_problems())
     return false;
@@ -435,7 +435,7 @@
 }
 
 bool CPDF_DataAvail::CheckHintTables() {
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   m_pHintTables =
       CPDF_HintTables::Parse(GetSyntaxParser(), m_pLinearized.get());
 
@@ -483,7 +483,7 @@
   if (m_bHeaderAvail)
     return DocAvailStatus::DataAvailable;
 
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   const Optional<FX_FILESIZE> header_offset = GetHeaderOffset(GetValidator());
   if (GetValidator()->has_read_problems())
     return DocAvailStatus::DataNotAvailable;
@@ -882,7 +882,7 @@
 CPDF_DataAvail::DocAvailStatus CPDF_DataAvail::CheckResources(
     CPDF_Dictionary* page) {
   ASSERT(page);
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   CPDF_Object* resources = GetResourceObject(page);
   if (GetValidator()->has_read_problems())
     return DocAvailStatus::DataNotAvailable;
@@ -1010,7 +1010,7 @@
                                                   std::move(pPageData));
   document->AddObserver(this);
 
-  CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   CPDF_Parser::Error error =
       document->LoadLinearizedDoc(GetValidator(), password);
 
diff --git a/core/fpdfapi/parser/cpdf_object_avail.cpp b/core/fpdfapi/parser/cpdf_object_avail.cpp
index 171c521..f4ed216 100644
--- a/core/fpdfapi/parser/cpdf_object_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_object_avail.cpp
@@ -60,7 +60,7 @@
       return true;
     }
 
-    const CPDF_ReadValidator::Session parse_session(validator_);
+    CPDF_ReadValidator::ScopedSession parse_session(validator_);
     CPDF_Object* direct = holder_->GetOrParseIndirectObject(ref_obj_num);
     if (validator_->has_read_problems())
       return false;
@@ -90,7 +90,7 @@
     if (!checked_objects.insert(obj_num).second)
       continue;
 
-    const CPDF_ReadValidator::Session parse_session(validator_);
+    CPDF_ReadValidator::ScopedSession parse_session(validator_);
     const CPDF_Object* direct = holder_->GetOrParseIndirectObject(obj_num);
     if (direct == root_)
       continue;
@@ -113,7 +113,7 @@
 
   CPDF_ObjectWalker walker(object);
   while (const CPDF_Object* obj = walker.GetNext()) {
-    const CPDF_ReadValidator::Session parse_session(validator_);
+    CPDF_ReadValidator::ScopedSession parse_session(validator_);
 
     // Skip if this object if it's an inlined root, the parent object or
     // explicitily excluded.
diff --git a/core/fpdfapi/parser/cpdf_read_validator.cpp b/core/fpdfapi/parser/cpdf_read_validator.cpp
index 9fca37f..b87d940 100644
--- a/core/fpdfapi/parser/cpdf_read_validator.cpp
+++ b/core/fpdfapi/parser/cpdf_read_validator.cpp
@@ -5,6 +5,7 @@
 #include "core/fpdfapi/parser/cpdf_read_validator.h"
 
 #include <algorithm>
+#include <utility>
 
 #include "core/fpdfapi/parser/cpdf_stream.h"
 #include "core/fxcrt/fx_safe_types.h"
@@ -26,16 +27,15 @@
 
 }  // namespace
 
-CPDF_ReadValidator::Session::Session(
-    const RetainPtr<CPDF_ReadValidator>& validator)
-    : validator_(validator.BackPointer()) {
-  ASSERT(validator_);
-  saved_read_error_ = validator_->read_error_;
-  saved_has_unavailable_data_ = validator_->has_unavailable_data_;
+CPDF_ReadValidator::ScopedSession::ScopedSession(
+    RetainPtr<CPDF_ReadValidator> validator)
+    : validator_(std::move(validator)),
+      saved_read_error_(validator_->read_error_),
+      saved_has_unavailable_data_(validator_->has_unavailable_data_) {
   validator_->ResetErrors();
 }
 
-CPDF_ReadValidator::Session::~Session() {
+CPDF_ReadValidator::ScopedSession::~ScopedSession() {
   validator_->read_error_ |= saved_read_error_;
   validator_->has_unavailable_data_ |= saved_has_unavailable_data_;
 }
@@ -45,9 +45,6 @@
     CPDF_DataAvail::FileAvail* file_avail)
     : file_read_(file_read),
       file_avail_(file_avail),
-      read_error_(false),
-      has_unavailable_data_(false),
-      whole_file_already_available_(false),
       file_size_(file_read->GetSize()) {}
 
 CPDF_ReadValidator::~CPDF_ReadValidator() = default;
diff --git a/core/fpdfapi/parser/cpdf_read_validator.h b/core/fpdfapi/parser/cpdf_read_validator.h
index e330661..4119d29 100644
--- a/core/fpdfapi/parser/cpdf_read_validator.h
+++ b/core/fpdfapi/parser/cpdf_read_validator.h
@@ -11,15 +11,21 @@
 
 class CPDF_ReadValidator : public IFX_SeekableReadStream {
  public:
-  class Session {
+  class ScopedSession {
    public:
-    explicit Session(const RetainPtr<CPDF_ReadValidator>& validator);
-    ~Session();
+    explicit ScopedSession(RetainPtr<CPDF_ReadValidator> validator);
+    ScopedSession(const ScopedSession& that) = delete;
+    ScopedSession& operator=(const ScopedSession& that) = delete;
+    ~ScopedSession();
 
    private:
-    UnownedPtr<CPDF_ReadValidator> validator_;
-    bool saved_read_error_;
-    bool saved_has_unavailable_data_;
+    // Make stack-allocated.
+    void* operator new(size_t) = delete;
+    void* operator new(size_t, void*) = delete;
+
+    RetainPtr<CPDF_ReadValidator> const validator_;
+    const bool saved_read_error_;
+    const bool saved_has_unavailable_data_;
   };
 
   CONSTRUCT_VIA_MAKE_RETAIN;
@@ -34,9 +40,7 @@
   }
 
   void ResetErrors();
-
   bool IsWholeFileAvailable();
-
   bool CheckDataRangeAndRequestIfUnavailable(FX_FILESIZE offset, size_t size);
   bool CheckWholeFileAndRequestIfUnavailable();
 
@@ -55,14 +59,12 @@
   void ScheduleDownload(FX_FILESIZE offset, size_t size);
   bool IsDataRangeAvailable(FX_FILESIZE offset, size_t size) const;
 
-  RetainPtr<IFX_SeekableReadStream> file_read_;
-  UnownedPtr<CPDF_DataAvail::FileAvail> file_avail_;
-
+  RetainPtr<IFX_SeekableReadStream> const file_read_;
+  UnownedPtr<CPDF_DataAvail::FileAvail> const file_avail_;
   UnownedPtr<CPDF_DataAvail::DownloadHints> hints_;
-
-  bool read_error_;
-  bool has_unavailable_data_;
-  bool whole_file_already_available_;
+  bool read_error_ = false;
+  bool has_unavailable_data_ = false;
+  bool whole_file_already_available_ = false;
   const FX_FILESIZE file_size_;
 };
 
diff --git a/core/fpdfapi/parser/cpdf_read_validator_unittest.cpp b/core/fpdfapi/parser/cpdf_read_validator_unittest.cpp
index d3d019c..abc8603 100644
--- a/core/fpdfapi/parser/cpdf_read_validator_unittest.cpp
+++ b/core/fpdfapi/parser/cpdf_read_validator_unittest.cpp
@@ -169,7 +169,7 @@
   auto validator = pdfium::MakeRetain<CPDF_ReadValidator>(file, &file_avail);
   validator->SetDownloadHints(&hints);
 
-  const CPDF_ReadValidator::Session read_session(validator);
+  CPDF_ReadValidator::ScopedSession read_session(validator);
   ASSERT_FALSE(validator->has_read_problems());
 
   // Data is unavailable
@@ -180,7 +180,7 @@
   EXPECT_FALSE(validator->read_error());
 
   {
-    const CPDF_ReadValidator::Session read_subsession(validator);
+    CPDF_ReadValidator::ScopedSession read_subsession(validator);
     // The read problems should be hidden.
     EXPECT_FALSE(validator->has_read_problems());
 
@@ -207,7 +207,7 @@
   auto validator = pdfium::MakeRetain<CPDF_ReadValidator>(file, &file_avail);
   validator->SetDownloadHints(&hints);
 
-  const CPDF_ReadValidator::Session read_session(validator);
+  CPDF_ReadValidator::ScopedSession read_session(validator);
   ASSERT_FALSE(validator->has_read_problems());
 
   // Data is unavailable
@@ -218,7 +218,7 @@
   EXPECT_FALSE(validator->read_error());
 
   {
-    const CPDF_ReadValidator::Session read_subsession(validator);
+    CPDF_ReadValidator::ScopedSession read_subsession(validator);
     // The read problems should be hidden.
     EXPECT_FALSE(validator->has_read_problems());
 
diff --git a/core/fpdfapi/parser/cpdf_syntax_parser.cpp b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
index 5318efd..f8bf219 100644
--- a/core/fpdfapi/parser/cpdf_syntax_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
@@ -465,7 +465,7 @@
 }
 
 ByteString CPDF_SyntaxParser::GetNextWord(bool* bIsNumber) {
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   GetNextWordInternal(bIsNumber);
   ByteString ret;
   if (!GetValidator()->has_read_problems())
@@ -488,7 +488,7 @@
 
 RetainPtr<CPDF_Object> CPDF_SyntaxParser::GetObjectBody(
     CPDF_IndirectObjectHolder* pObjList) {
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   auto result = GetObjectBodyInternal(pObjList, ParseType::kLoose);
   if (GetValidator()->has_read_problems())
     return nullptr;
@@ -609,7 +609,7 @@
 RetainPtr<CPDF_Object> CPDF_SyntaxParser::GetIndirectObject(
     CPDF_IndirectObjectHolder* pObjList,
     ParseType parse_type) {
-  const CPDF_ReadValidator::Session read_session(GetValidator());
+  CPDF_ReadValidator::ScopedSession read_session(GetValidator());
   const FX_FILESIZE saved_pos = GetPos();
   bool is_number = false;
   ByteString word = GetNextWord(&is_number);
@@ -742,7 +742,7 @@
   // Note, we allow zero length streams as we need to pass them through when we
   // are importing pages into a new document.
   if (len >= 0) {
-    const CPDF_ReadValidator::Session read_session(GetValidator());
+    CPDF_ReadValidator::ScopedSession read_session(GetValidator());
     m_Pos += ReadEOLMarkers(GetPos());
     memset(m_WordBuffer, 0, kEndStreamStr.GetLength() + 1);
     GetNextWordInternal(nullptr);