Disallow dereferencing deferred handles when generating optimized code.

src/handles.h

Index: src/handles.h
diff --git a/src/handles.h b/src/handles.h
index 8e9404cb9d105024578fa92b18e140a2a15d0dc0..938d43b8a4e8ba418f85b7eb5ccd2a5ccfb6aad3 100644
--- a/src/handles.h
+++ b/src/handles.h
@@ -73,8 +73,8 @@ class Handle {
   INLINE(T** location() const);
 
   template <class S> static Handle<T> cast(Handle<S> that) {
-    T::cast(*that);
-    return Handle<T>(reinterpret_cast<T**>(that.location()));
+    T::cast(*reinterpret_cast<T**>(that.location_));
+    return Handle<T>(reinterpret_cast<T**>(that.location_));
   }
 
   static Handle<T> null() { return Handle<T>(); }
@@ -84,6 +84,10 @@ class Handle {
   // implementation in api.h.
   inline Handle<T> EscapeFrom(v8::HandleScope* scope);
 
+#ifdef DEBUG
+  bool IsDereferenceAllowed(bool allow_deferred) const;
+#endif  // DEBUG
+
  private:
   T** location_;
 
@@ -341,7 +345,7 @@ class NoHandleAllocation BASE_EMBEDDED {
 
 class HandleDereferenceGuard BASE_EMBEDDED {
  public:
-  enum State { ALLOW, DISALLOW };
+  enum State { ALLOW, DISALLOW, DISALLOW_DEFERRED };
 #ifndef DEBUG
   HandleDereferenceGuard(Isolate* isolate, State state) { }
   ~HandleDereferenceGuard() { }
@@ -350,10 +354,18 @@ class HandleDereferenceGuard BASE_EMBEDDED {
   inline ~HandleDereferenceGuard();
  private:
   Isolate* isolate_;
-  bool old_state_;
+  State old_state_;
 #endif
 };
 
+#ifdef DEBUG
+#define ALLOW_HANDLE_DEREF(isolate, why_this_is_safe)                          \
+  HandleDereferenceGuard allow_deref(isolate,                                  \
+                                     HandleDereferenceGuard::ALLOW);
+#else
+#define ALLOW_HANDLE_DEREF(isolate, why_this_is_safe)
+#endif  // DEBUG
+
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_H_