Disallow dereferencing deferred handles when generating optimized code.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 9e0293d210f04bc532e3a04c98d04470721d2917..fe5e57151b55fe20897fa99894564677016c2589 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -991,9 +991,9 @@ class Isolate {
 
   int* code_kind_statistics() { return code_kind_statistics_; }
 
-  bool AllowHandleDereference();
+  HandleDereferenceGuard::State HandleDereferenceGuardState();
 
-  void SetAllowHandleDereference(bool allow);
+  void SetHandleDereferenceGuardState(HandleDereferenceGuard::State state);
 #endif
 
 #if defined(V8_TARGET_ARCH_ARM) && !defined(__arm__) || \
@@ -1074,6 +1074,10 @@ class Isolate {
   void LinkDeferredHandles(DeferredHandles* deferred_handles);
   void UnlinkDeferredHandles(DeferredHandles* deferred_handles);
 
+#ifdef DEBUG
+  bool IsDeferredHandle(Object** location);
+#endif  // DEBUG
+
   OptimizingCompilerThread* optimizing_compiler_thread() {
     return &optimizing_compiler_thread_;
   }
@@ -1292,8 +1296,8 @@ class Isolate {
   JSObject::SpillInformation js_spill_information_;
   int code_kind_statistics_[Code::NUMBER_OF_KINDS];
 
-  bool allow_compiler_thread_handle_deref_;
-  bool allow_execution_thread_handle_deref_;
+  HandleDereferenceGuard::State compiler_thread_handle_deref_state_;
+  HandleDereferenceGuard::State execution_thread_handle_deref_state_;
 #endif
 
 #ifdef ENABLE_DEBUGGER_SUPPORT