Tag XFA data bound to V8 Objects.

Because we don't want to trust anything V8 gives us back.
Use a deep namespace so we can have a short declaration in the
structs, but avoid collisions.

Change-Id: Ibb832a5dcd34c652159c3343dd70c9e2ee561537
Reviewed-on: https://pdfium-review.googlesource.com/38972
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

5 files changed, 157 insertions, 110 deletions

diff --git a/fxjs/cfxjse_class.cpp b/fxjs/cfxjse_class.cpp
index 67186ff66f..e7e54c8867 100644
--- a/fxjs/cfxjse_class.cpp
+++ b/fxjs/cfxjse_class.cpp
@@ -16,13 +16,25 @@
 #include "fxjs/js_resources.h"
 #include "third_party/base/ptr_util.h"
 
+using pdfium::fxjse::kFuncTag;
+using pdfium::fxjse::kClassTag;
+
 namespace {
 
+FXJSE_FUNCTION_DESCRIPTOR* AsFunctionDescriptor(void* ptr) {
+  auto* result = static_cast<FXJSE_FUNCTION_DESCRIPTOR*>(ptr);
+  return result && result->tag == kFuncTag ? result : nullptr;
+}
+
+FXJSE_CLASS_DESCRIPTOR* AsClassDescriptor(void* ptr) {
+  auto* result = static_cast<FXJSE_CLASS_DESCRIPTOR*>(ptr);
+  return result && result->tag == kClassTag ? result : nullptr;
+}
+
 void V8FunctionCallback_Wrapper(
     const v8::FunctionCallbackInfo<v8::Value>& info) {
   const FXJSE_FUNCTION_DESCRIPTOR* lpFunctionInfo =
-      static_cast<FXJSE_FUNCTION_DESCRIPTOR*>(
-          info.Data().As<v8::External>()->Value());
+      AsFunctionDescriptor(info.Data().As<v8::External>()->Value());
   if (!lpFunctionInfo)
     return;
 
@@ -42,8 +54,7 @@ void V8ConstructorCallback_Wrapper(
     return;
 
   const FXJSE_CLASS_DESCRIPTOR* lpClassDefinition =
-      static_cast<FXJSE_CLASS_DESCRIPTOR*>(
-          info.Data().As<v8::External>()->Value());
+      AsClassDescriptor(info.Data().As<v8::External>()->Value());
   if (!lpClassDefinition)
     return;
 
@@ -54,8 +65,8 @@ void V8ConstructorCallback_Wrapper(
 
 void Context_GlobalObjToString(
     const v8::FunctionCallbackInfo<v8::Value>& info) {
-  const FXJSE_CLASS_DESCRIPTOR* lpClass = static_cast<FXJSE_CLASS_DESCRIPTOR*>(
-      info.Data().As<v8::External>()->Value());
+  const FXJSE_CLASS_DESCRIPTOR* lpClass =
+      AsClassDescriptor(info.Data().As<v8::External>()->Value());
   if (!lpClass)
     return;
 
@@ -178,11 +189,13 @@ void NamedPropertyQueryCallback(
     v8::Local<v8::Name> property,
     const v8::PropertyCallbackInfo<v8::Integer>& info) {
   v8::Local<v8::Object> thisObject = info.Holder();
-  const FXJSE_CLASS_DESCRIPTOR* lpClass = static_cast<FXJSE_CLASS_DESCRIPTOR*>(
-      info.Data().As<v8::External>()->Value());
-  v8::Isolate* pIsolate = info.GetIsolate();
-  v8::HandleScope scope(pIsolate);
-  v8::String::Utf8Value szPropName(pIsolate, property);
+  const FXJSE_CLASS_DESCRIPTOR* lpClass =
+      AsClassDescriptor(info.Data().As<v8::External>()->Value());
+  if (!lpClass)
+    return;
+
+  v8::HandleScope scope(info.GetIsolate());
+  v8::String::Utf8Value szPropName(info.GetIsolate(), property);
   ByteStringView szFxPropName(*szPropName, szPropName.length());
   auto lpThisValue = pdfium::MakeUnique<CFXJSE_Value>(info.GetIsolate());
   lpThisValue->ForceSetValue(thisObject);
@@ -198,8 +211,11 @@ void NamedPropertyGetterCallback(
     v8::Local<v8::Name> property,
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   v8::Local<v8::Object> thisObject = info.Holder();
-  const FXJSE_CLASS_DESCRIPTOR* lpClass = static_cast<FXJSE_CLASS_DESCRIPTOR*>(
-      info.Data().As<v8::External>()->Value());
+  const FXJSE_CLASS_DESCRIPTOR* lpClass =
+      AsClassDescriptor(info.Data().As<v8::External>()->Value());
+  if (!lpClass)
+    return;
+
   v8::String::Utf8Value szPropName(info.GetIsolate(), property);
   ByteStringView szFxPropName(*szPropName, szPropName.length());
   auto lpThisValue = pdfium::MakeUnique<CFXJSE_Value>(info.GetIsolate());
@@ -215,13 +231,15 @@ void NamedPropertySetterCallback(
     v8::Local<v8::Value> value,
     const v8::PropertyCallbackInfo<v8::Value>& info) {
   v8::Local<v8::Object> thisObject = info.Holder();
-  const FXJSE_CLASS_DESCRIPTOR* lpClass = static_cast<FXJSE_CLASS_DESCRIPTOR*>(
-      info.Data().As<v8::External>()->Value());
+  const FXJSE_CLASS_DESCRIPTOR* lpClass =
+      AsClassDescriptor(info.Data().As<v8::External>()->Value());
+  if (!lpClass)
+    return;
+
   v8::String::Utf8Value szPropName(info.GetIsolate(), property);
   ByteStringView szFxPropName(*szPropName, szPropName.length());
   auto lpThisValue = pdfium::MakeUnique<CFXJSE_Value>(info.GetIsolate());
   lpThisValue->ForceSetValue(thisObject);
-
   auto lpNewValue = pdfium::MakeUnique<CFXJSE_Value>(info.GetIsolate());
   lpNewValue->ForceSetValue(value);
   DynPropSetterAdapter(lpClass, lpThisValue.get(), szFxPropName,
diff --git a/fxjs/cfxjse_engine.cpp b/fxjs/cfxjse_engine.cpp
index cc584a3fa3..bf5778bf9a 100644
--- a/fxjs/cfxjse_engine.cpp
+++ b/fxjs/cfxjse_engine.cpp
@@ -31,10 +31,13 @@
 #include "xfa/fxfa/parser/xfa_resolvenode_rs.h"
 #include "xfa/fxfa/parser/xfa_utils.h"
 
+using pdfium::fxjse::kClassTag;
+
 const FXJSE_CLASS_DESCRIPTOR GlobalClassDescriptor = {
-    "Root",   // name
-    nullptr,  // methods
-    0,        // method count
+    kClassTag,  // tag
+    "Root",     // name
+    nullptr,    // methods
+    0,          // method count
     CFXJSE_Engine::GlobalPropTypeGetter,
     CFXJSE_Engine::GlobalPropertyGetter,
     CFXJSE_Engine::GlobalPropertySetter,
@@ -42,6 +45,7 @@ const FXJSE_CLASS_DESCRIPTOR GlobalClassDescriptor = {
 };
 
 const FXJSE_CLASS_DESCRIPTOR NormalClassDescriptor = {
+    kClassTag,    // tag
     "XFAObject",  // name
     nullptr,      // methods
     0,            // method count
@@ -52,6 +56,7 @@ const FXJSE_CLASS_DESCRIPTOR NormalClassDescriptor = {
 };
 
 const FXJSE_CLASS_DESCRIPTOR VariablesClassDescriptor = {
+    kClassTag,          // tag
     "XFAScriptObject",  // name
     nullptr,            // methods
     0,                  // method count
diff --git a/fxjs/cfxjse_formcalc_context.cpp b/fxjs/cfxjse_formcalc_context.cpp
index 5319466cfa..40f4249ab7 100644
--- a/fxjs/cfxjse_formcalc_context.cpp
+++ b/fxjs/cfxjse_formcalc_context.cpp
@@ -32,6 +32,9 @@
 #include "xfa/fxfa/parser/cxfa_timezoneprovider.h"
 #include "xfa/fxfa/parser/xfa_utils.h"
 
+using pdfium::fxjse::kFuncTag;
+using pdfium::fxjse::kClassTag;
+
 namespace {
 
 const double kFinancialPrecision = 0.00000001;
@@ -218,97 +221,97 @@ const XFA_FMHtmlReserveCode kReservesForEncode[] = {
 };
 
 const FXJSE_FUNCTION_DESCRIPTOR kFormCalcFM2JSFunctions[] = {
-    {"Abs", CFXJSE_FormCalcContext::Abs},
-    {"Avg", CFXJSE_FormCalcContext::Avg},
-    {"Ceil", CFXJSE_FormCalcContext::Ceil},
-    {"Count", CFXJSE_FormCalcContext::Count},
-    {"Floor", CFXJSE_FormCalcContext::Floor},
-    {"Max", CFXJSE_FormCalcContext::Max},
-    {"Min", CFXJSE_FormCalcContext::Min},
-    {"Mod", CFXJSE_FormCalcContext::Mod},
-    {"Round", CFXJSE_FormCalcContext::Round},
-    {"Sum", CFXJSE_FormCalcContext::Sum},
-    {"Date", CFXJSE_FormCalcContext::Date},
-    {"Date2Num", CFXJSE_FormCalcContext::Date2Num},
-    {"DateFmt", CFXJSE_FormCalcContext::DateFmt},
-    {"IsoDate2Num", CFXJSE_FormCalcContext::IsoDate2Num},
-    {"IsoTime2Num", CFXJSE_FormCalcContext::IsoTime2Num},
-    {"LocalDateFmt", CFXJSE_FormCalcContext::LocalDateFmt},
-    {"LocalTimeFmt", CFXJSE_FormCalcContext::LocalTimeFmt},
-    {"Num2Date", CFXJSE_FormCalcContext::Num2Date},
-    {"Num2GMTime", CFXJSE_FormCalcContext::Num2GMTime},
-    {"Num2Time", CFXJSE_FormCalcContext::Num2Time},
-    {"Time", CFXJSE_FormCalcContext::Time},
-    {"Time2Num", CFXJSE_FormCalcContext::Time2Num},
-    {"TimeFmt", CFXJSE_FormCalcContext::TimeFmt},
-    {"Apr", CFXJSE_FormCalcContext::Apr},
-    {"Cterm", CFXJSE_FormCalcContext::CTerm},
-    {"FV", CFXJSE_FormCalcContext::FV},
-    {"Ipmt", CFXJSE_FormCalcContext::IPmt},
-    {"NPV", CFXJSE_FormCalcContext::NPV},
-    {"Pmt", CFXJSE_FormCalcContext::Pmt},
-    {"PPmt", CFXJSE_FormCalcContext::PPmt},
-    {"PV", CFXJSE_FormCalcContext::PV},
-    {"Rate", CFXJSE_FormCalcContext::Rate},
-    {"Term", CFXJSE_FormCalcContext::Term},
-    {"Choose", CFXJSE_FormCalcContext::Choose},
-    {"Exists", CFXJSE_FormCalcContext::Exists},
-    {"HasValue", CFXJSE_FormCalcContext::HasValue},
-    {"Oneof", CFXJSE_FormCalcContext::Oneof},
-    {"Within", CFXJSE_FormCalcContext::Within},
-    {"If", CFXJSE_FormCalcContext::If},
-    {"Eval", CFXJSE_FormCalcContext::Eval},
-    {"Translate", CFXJSE_FormCalcContext::eval_translation},
-    {"Ref", CFXJSE_FormCalcContext::Ref},
-    {"UnitType", CFXJSE_FormCalcContext::UnitType},
-    {"UnitValue", CFXJSE_FormCalcContext::UnitValue},
-    {"At", CFXJSE_FormCalcContext::At},
-    {"Concat", CFXJSE_FormCalcContext::Concat},
-    {"Decode", CFXJSE_FormCalcContext::Decode},
-    {"Encode", CFXJSE_FormCalcContext::Encode},
-    {"Format", CFXJSE_FormCalcContext::Format},
-    {"Left", CFXJSE_FormCalcContext::Left},
-    {"Len", CFXJSE_FormCalcContext::Len},
-    {"Lower", CFXJSE_FormCalcContext::Lower},
-    {"Ltrim", CFXJSE_FormCalcContext::Ltrim},
-    {"Parse", CFXJSE_FormCalcContext::Parse},
-    {"Replace", CFXJSE_FormCalcContext::Replace},
-    {"Right", CFXJSE_FormCalcContext::Right},
-    {"Rtrim", CFXJSE_FormCalcContext::Rtrim},
-    {"Space", CFXJSE_FormCalcContext::Space},
-    {"Str", CFXJSE_FormCalcContext::Str},
-    {"Stuff", CFXJSE_FormCalcContext::Stuff},
-    {"Substr", CFXJSE_FormCalcContext::Substr},
-    {"Uuid", CFXJSE_FormCalcContext::Uuid},
-    {"Upper", CFXJSE_FormCalcContext::Upper},
-    {"WordNum", CFXJSE_FormCalcContext::WordNum},
-    {"Get", CFXJSE_FormCalcContext::Get},
-    {"Post", CFXJSE_FormCalcContext::Post},
-    {"Put", CFXJSE_FormCalcContext::Put},
-    {"pos_op", CFXJSE_FormCalcContext::positive_operator},
-    {"neg_op", CFXJSE_FormCalcContext::negative_operator},
-    {"log_or_op", CFXJSE_FormCalcContext::logical_or_operator},
-    {"log_and_op", CFXJSE_FormCalcContext::logical_and_operator},
-    {"log_not_op", CFXJSE_FormCalcContext::logical_not_operator},
-    {"eq_op", CFXJSE_FormCalcContext::equality_operator},
-    {"neq_op", CFXJSE_FormCalcContext::notequality_operator},
-    {"lt_op", CFXJSE_FormCalcContext::less_operator},
-    {"le_op", CFXJSE_FormCalcContext::lessequal_operator},
-    {"gt_op", CFXJSE_FormCalcContext::greater_operator},
-    {"ge_op", CFXJSE_FormCalcContext::greaterequal_operator},
-    {"plus_op", CFXJSE_FormCalcContext::plus_operator},
-    {"minus_op", CFXJSE_FormCalcContext::minus_operator},
-    {"mul_op", CFXJSE_FormCalcContext::multiple_operator},
-    {"div_op", CFXJSE_FormCalcContext::divide_operator},
-    {"asgn_val_op", CFXJSE_FormCalcContext::assign_value_operator},
-    {"dot_acc", CFXJSE_FormCalcContext::dot_accessor},
-    {"dotdot_acc", CFXJSE_FormCalcContext::dotdot_accessor},
-    {"concat_obj", CFXJSE_FormCalcContext::concat_fm_object},
-    {"is_obj", CFXJSE_FormCalcContext::is_fm_object},
-    {"is_ary", CFXJSE_FormCalcContext::is_fm_array},
-    {"get_val", CFXJSE_FormCalcContext::get_fm_value},
-    {"get_jsobj", CFXJSE_FormCalcContext::get_fm_jsobj},
-    {"var_filter", CFXJSE_FormCalcContext::fm_var_filter},
+    {kFuncTag, "Abs", CFXJSE_FormCalcContext::Abs},
+    {kFuncTag, "Avg", CFXJSE_FormCalcContext::Avg},
+    {kFuncTag, "Ceil", CFXJSE_FormCalcContext::Ceil},
+    {kFuncTag, "Count", CFXJSE_FormCalcContext::Count},
+    {kFuncTag, "Floor", CFXJSE_FormCalcContext::Floor},
+    {kFuncTag, "Max", CFXJSE_FormCalcContext::Max},
+    {kFuncTag, "Min", CFXJSE_FormCalcContext::Min},
+    {kFuncTag, "Mod", CFXJSE_FormCalcContext::Mod},
+    {kFuncTag, "Round", CFXJSE_FormCalcContext::Round},
+    {kFuncTag, "Sum", CFXJSE_FormCalcContext::Sum},
+    {kFuncTag, "Date", CFXJSE_FormCalcContext::Date},
+    {kFuncTag, "Date2Num", CFXJSE_FormCalcContext::Date2Num},
+    {kFuncTag, "DateFmt", CFXJSE_FormCalcContext::DateFmt},
+    {kFuncTag, "IsoDate2Num", CFXJSE_FormCalcContext::IsoDate2Num},
+    {kFuncTag, "IsoTime2Num", CFXJSE_FormCalcContext::IsoTime2Num},
+    {kFuncTag, "LocalDateFmt", CFXJSE_FormCalcContext::LocalDateFmt},
+    {kFuncTag, "LocalTimeFmt", CFXJSE_FormCalcContext::LocalTimeFmt},
+    {kFuncTag, "Num2Date", CFXJSE_FormCalcContext::Num2Date},
+    {kFuncTag, "Num2GMTime", CFXJSE_FormCalcContext::Num2GMTime},
+    {kFuncTag, "Num2Time", CFXJSE_FormCalcContext::Num2Time},
+    {kFuncTag, "Time", CFXJSE_FormCalcContext::Time},
+    {kFuncTag, "Time2Num", CFXJSE_FormCalcContext::Time2Num},
+    {kFuncTag, "TimeFmt", CFXJSE_FormCalcContext::TimeFmt},
+    {kFuncTag, "Apr", CFXJSE_FormCalcContext::Apr},
+    {kFuncTag, "Cterm", CFXJSE_FormCalcContext::CTerm},
+    {kFuncTag, "FV", CFXJSE_FormCalcContext::FV},
+    {kFuncTag, "Ipmt", CFXJSE_FormCalcContext::IPmt},
+    {kFuncTag, "NPV", CFXJSE_FormCalcContext::NPV},
+    {kFuncTag, "Pmt", CFXJSE_FormCalcContext::Pmt},
+    {kFuncTag, "PPmt", CFXJSE_FormCalcContext::PPmt},
+    {kFuncTag, "PV", CFXJSE_FormCalcContext::PV},
+    {kFuncTag, "Rate", CFXJSE_FormCalcContext::Rate},
+    {kFuncTag, "Term", CFXJSE_FormCalcContext::Term},
+    {kFuncTag, "Choose", CFXJSE_FormCalcContext::Choose},
+    {kFuncTag, "Exists", CFXJSE_FormCalcContext::Exists},
+    {kFuncTag, "HasValue", CFXJSE_FormCalcContext::HasValue},
+    {kFuncTag, "Oneof", CFXJSE_FormCalcContext::Oneof},
+    {kFuncTag, "Within", CFXJSE_FormCalcContext::Within},
+    {kFuncTag, "If", CFXJSE_FormCalcContext::If},
+    {kFuncTag, "Eval", CFXJSE_FormCalcContext::Eval},
+    {kFuncTag, "Translate", CFXJSE_FormCalcContext::eval_translation},
+    {kFuncTag, "Ref", CFXJSE_FormCalcContext::Ref},
+    {kFuncTag, "UnitType", CFXJSE_FormCalcContext::UnitType},
+    {kFuncTag, "UnitValue", CFXJSE_FormCalcContext::UnitValue},
+    {kFuncTag, "At", CFXJSE_FormCalcContext::At},
+    {kFuncTag, "Concat", CFXJSE_FormCalcContext::Concat},
+    {kFuncTag, "Decode", CFXJSE_FormCalcContext::Decode},
+    {kFuncTag, "Encode", CFXJSE_FormCalcContext::Encode},
+    {kFuncTag, "Format", CFXJSE_FormCalcContext::Format},
+    {kFuncTag, "Left", CFXJSE_FormCalcContext::Left},
+    {kFuncTag, "Len", CFXJSE_FormCalcContext::Len},
+    {kFuncTag, "Lower", CFXJSE_FormCalcContext::Lower},
+    {kFuncTag, "Ltrim", CFXJSE_FormCalcContext::Ltrim},
+    {kFuncTag, "Parse", CFXJSE_FormCalcContext::Parse},
+    {kFuncTag, "Replace", CFXJSE_FormCalcContext::Replace},
+    {kFuncTag, "Right", CFXJSE_FormCalcContext::Right},
+    {kFuncTag, "Rtrim", CFXJSE_FormCalcContext::Rtrim},
+    {kFuncTag, "Space", CFXJSE_FormCalcContext::Space},
+    {kFuncTag, "Str", CFXJSE_FormCalcContext::Str},
+    {kFuncTag, "Stuff", CFXJSE_FormCalcContext::Stuff},
+    {kFuncTag, "Substr", CFXJSE_FormCalcContext::Substr},
+    {kFuncTag, "Uuid", CFXJSE_FormCalcContext::Uuid},
+    {kFuncTag, "Upper", CFXJSE_FormCalcContext::Upper},
+    {kFuncTag, "WordNum", CFXJSE_FormCalcContext::WordNum},
+    {kFuncTag, "Get", CFXJSE_FormCalcContext::Get},
+    {kFuncTag, "Post", CFXJSE_FormCalcContext::Post},
+    {kFuncTag, "Put", CFXJSE_FormCalcContext::Put},
+    {kFuncTag, "pos_op", CFXJSE_FormCalcContext::positive_operator},
+    {kFuncTag, "neg_op", CFXJSE_FormCalcContext::negative_operator},
+    {kFuncTag, "log_or_op", CFXJSE_FormCalcContext::logical_or_operator},
+    {kFuncTag, "log_and_op", CFXJSE_FormCalcContext::logical_and_operator},
+    {kFuncTag, "log_not_op", CFXJSE_FormCalcContext::logical_not_operator},
+    {kFuncTag, "eq_op", CFXJSE_FormCalcContext::equality_operator},
+    {kFuncTag, "neq_op", CFXJSE_FormCalcContext::notequality_operator},
+    {kFuncTag, "lt_op", CFXJSE_FormCalcContext::less_operator},
+    {kFuncTag, "le_op", CFXJSE_FormCalcContext::lessequal_operator},
+    {kFuncTag, "gt_op", CFXJSE_FormCalcContext::greater_operator},
+    {kFuncTag, "ge_op", CFXJSE_FormCalcContext::greaterequal_operator},
+    {kFuncTag, "plus_op", CFXJSE_FormCalcContext::plus_operator},
+    {kFuncTag, "minus_op", CFXJSE_FormCalcContext::minus_operator},
+    {kFuncTag, "mul_op", CFXJSE_FormCalcContext::multiple_operator},
+    {kFuncTag, "div_op", CFXJSE_FormCalcContext::divide_operator},
+    {kFuncTag, "asgn_val_op", CFXJSE_FormCalcContext::assign_value_operator},
+    {kFuncTag, "dot_acc", CFXJSE_FormCalcContext::dot_accessor},
+    {kFuncTag, "dotdot_acc", CFXJSE_FormCalcContext::dotdot_accessor},
+    {kFuncTag, "concat_obj", CFXJSE_FormCalcContext::concat_fm_object},
+    {kFuncTag, "is_obj", CFXJSE_FormCalcContext::is_fm_object},
+    {kFuncTag, "is_ary", CFXJSE_FormCalcContext::is_fm_array},
+    {kFuncTag, "get_val", CFXJSE_FormCalcContext::get_fm_value},
+    {kFuncTag, "get_jsobj", CFXJSE_FormCalcContext::get_fm_jsobj},
+    {kFuncTag, "var_filter", CFXJSE_FormCalcContext::fm_var_filter},
 };
 
 const uint8_t kAltTableDate[] = {
@@ -607,6 +610,7 @@ double ByteStringToDouble(const ByteStringView& szStringVal) {
 }  // namespace
 
 const FXJSE_CLASS_DESCRIPTOR kFormCalcFM2JSDescriptor = {
+    kClassTag,                              // tag
     "XFA_FM2JS_FormCalcClass",              // name
     kFormCalcFM2JSFunctions,                // methods
     FX_ArraySize(kFormCalcFM2JSFunctions),  // number of methods
diff --git a/fxjs/fxjse.cpp b/fxjs/fxjse.cpp
index 68adaa5dd3..44849fdfec 100644
--- a/fxjs/fxjse.cpp
+++ b/fxjs/fxjse.cpp
@@ -6,6 +6,15 @@
 
 #include "fxjs/fxjse.h"
 
+namespace pdfium {
+namespace fxjse {
+
+const char kFuncTag[] = "function descriptor tag";
+const char kClassTag[] = "class descriptor tag";
+
+}  // namespace fxjse
+}  // namespace pdfium
+
 CFXJSE_HostObject::CFXJSE_HostObject() = default;
 
 CFXJSE_HostObject::~CFXJSE_HostObject() = default;
diff --git a/fxjs/fxjse.h b/fxjs/fxjse.h
index 3f2eb1d836..c28cc6c919 100644
--- a/fxjs/fxjse.h
+++ b/fxjs/fxjse.h
@@ -11,6 +11,15 @@
 #include "core/fxcrt/fx_system.h"
 #include "v8/include/v8.h"
 
+namespace pdfium {
+namespace fxjse {
+
+extern const char kFuncTag[];
+extern const char kClassTag[];
+
+}  // namespace fxjse
+}  // namespace pdfium
+
 class CFXJSE_Arguments;
 class CFXJSE_FormCalcContext;
 class CFXJSE_Value;
@@ -50,11 +59,13 @@ enum FXJSE_ClassPropTypes {
 };
 
 struct FXJSE_FUNCTION_DESCRIPTOR {
+  const char* tag;  // pdfium::kFuncTag always.
   const char* name;
   FXJSE_FuncCallback callbackProc;
 };
 
 struct FXJSE_CLASS_DESCRIPTOR {
+  const char* tag;  // pdfium::kClassTag always.
   const char* name;
   const FXJSE_FUNCTION_DESCRIPTOR* methods;
   int32_t methNum;