Make non-Module generators only context allocate parameters.

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index dad43db911f62de4aa469268b214c712f988195c..533268fab5cfc2f7ebe60223afe0d2659502543e 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -348,6 +348,7 @@ void Scope::SetDefaults() {
 
   inner_scope_calls_eval_ = false;
   force_context_allocation_ = false;
+  force_context_allocation_for_parameters_ = false;
 
   is_declaration_scope_ = false;
 
@@ -2193,7 +2194,8 @@ void DeclarationScope::AllocateParameterLocals() {
 
 void DeclarationScope::AllocateParameter(Variable* var, int index) {
   if (MustAllocate(var)) {
-    if (MustAllocateInContext(var)) {
+    if (has_forced_context_allocation_for_parameters() ||
+        MustAllocateInContext(var)) {
       DCHECK(var->IsUnallocated() || var->IsContextSlot());
       if (var->IsUnallocated()) {
         AllocateHeapSlot(var);