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

src/debug/debug-scopes.cc

Index: src/debug/debug-scopes.cc
diff --git a/src/debug/debug-scopes.cc b/src/debug/debug-scopes.cc
index 3ef7eedfedd983fd247e559ac91ff3e4f9cc3ff4..1f59451a7d7e0418e76310db5976cf4e7223778b 100644
--- a/src/debug/debug-scopes.cc
+++ b/src/debug/debug-scopes.cc
@@ -801,19 +801,16 @@ void ScopeIterator::CopyContextLocalsToScopeObject(
   int local_count = scope_info->ContextLocalCount();
   if (local_count == 0) return;
   // Fill all context locals to the context extension.
-  int first_context_var = scope_info->StackLocalCount();
-  int start = scope_info->ContextLocalNameEntriesIndex();
   for (int i = 0; i < local_count; ++i) {
-    if (scope_info->LocalIsSynthetic(first_context_var + i)) continue;
+    Handle<String> name(scope_info->ContextLocalName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     int context_index = Context::MIN_CONTEXT_SLOTS + i;
     Handle<Object> value = Handle<Object>(context->get(context_index), isolate);
     // Reflect variables under TDZ as undefined in scope object.
     if (value->IsTheHole()) continue;
     // This should always succeed.
     // TODO(verwaest): Use AddDataProperty instead.
-    JSObject::SetOwnPropertyIgnoreAttributes(
-        scope_object, handle(String::cast(scope_info->get(i + start))), value,
-        NONE)
+    JSObject::SetOwnPropertyIgnoreAttributes(scope_object, name, value, NONE)
         .Check();
   }
 }