[debugger] do not expose temporary variables introduced by the parser.

test/mjsunit/es6/debug-blockscopes.js

Index: test/mjsunit/es6/debug-blockscopes.js
diff --git a/test/mjsunit/es6/debug-blockscopes.js b/test/mjsunit/es6/debug-blockscopes.js
index 87dd1b66c889d50a63d431375694573309622ff7..bf04a0a4aae3e64a8d4c35c5283a81a38b6e6056 100644
--- a/test/mjsunit/es6/debug-blockscopes.js
+++ b/test/mjsunit/es6/debug-blockscopes.js
@@ -148,10 +148,8 @@ function CheckScopeContent(content, number, exec_state) {
   if (!scope.scopeObject().property('arguments').isUndefined()) {
     scope_size--;
   }
-  // Skip property with empty name.
-  if (!scope.scopeObject().property('').isUndefined()) {
-    scope_size--;
-  }
+  // Temporary variables introduced by the parser have not been materialized.
+  assertTrue(scope.scopeObject().property('').isUndefined());
 
   if (count != scope_size) {
     print('Names found in scope:');