Revert of [d8] bounds-check before getting Shell::Worker internal field

src/d8.cc

Index: src/d8.cc
diff --git a/src/d8.cc b/src/d8.cc
index 2117825ef4b77b5f89d66934bd3471086e42fd12..7db6f3ed9e442081528e05140bd25b8911e26cb6 100644
--- a/src/d8.cc
+++ b/src/d8.cc
@@ -717,17 +717,14 @@
   Isolate* isolate = args.GetIsolate();
   HandleScope handle_scope(isolate);
   Local<Context> context = isolate->GetCurrentContext();
-  Local<Value> this_value;
 
   if (args.Length() < 1) {
     Throw(isolate, "Invalid argument");
     return;
   }
 
-  if (args.This()->InternalFieldCount() > 0) {
-    this_value = args.This()->GetInternalField(0);
-  }
-  if (this_value.IsEmpty()) {
+  Local<Value> this_value = args.This()->GetInternalField(0);
+  if (!this_value->IsExternal()) {
     Throw(isolate, "this is not a Worker");
     return;
   }
@@ -773,11 +770,9 @@
 void Shell::WorkerGetMessage(const v8::FunctionCallbackInfo<v8::Value>& args) {
   Isolate* isolate = args.GetIsolate();
   HandleScope handle_scope(isolate);
-  Local<Value> this_value;
-  if (args.This()->InternalFieldCount() > 0) {
-    this_value = args.This()->GetInternalField(0);
-  }
-  if (this_value.IsEmpty()) {
+
+  Local<Value> this_value = args.This()->GetInternalField(0);
+  if (!this_value->IsExternal()) {
     Throw(isolate, "this is not a Worker");
     return;
   }
@@ -800,11 +795,8 @@
 void Shell::WorkerTerminate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   Isolate* isolate = args.GetIsolate();
   HandleScope handle_scope(isolate);
-  Local<Value> this_value;
-  if (args.This()->InternalFieldCount() > 0) {
-    this_value = args.This()->GetInternalField(0);
-  }
-  if (this_value.IsEmpty()) {
+  Local<Value> this_value = args.This()->GetInternalField(0);
+  if (!this_value->IsExternal()) {
     Throw(isolate, "this is not a Worker");
     return;
   }