Use a different map to distinguish eval contexts

src/runtime/runtime-scopes.cc

Index: src/runtime/runtime-scopes.cc
diff --git a/src/runtime/runtime-scopes.cc b/src/runtime/runtime-scopes.cc
index 0c037db307a60ca994da643e9a2554b462654ced..e6de242b227f8afc3ac4e8ed282b980ff7535c2a 100644
--- a/src/runtime/runtime-scopes.cc
+++ b/src/runtime/runtime-scopes.cc
@@ -232,7 +232,7 @@ Object* DeclareEvalHelper(Isolate* isolate, Handle<String> name,
   Handle<Context> context(context_arg->declaration_context(), isolate);
 
   DCHECK(context->IsFunctionContext() || context->IsNativeContext() ||
-         context->IsScriptContext() ||
+         context->IsScriptContext() || context->IsEvalContext() ||
          (context->IsBlockContext() && context->has_extension()));
 
   bool is_function = value->IsJSFunction();
@@ -313,7 +313,7 @@ Object* DeclareEvalHelper(Isolate* isolate, Handle<String> name,
     }
     DCHECK(object->IsJSContextExtensionObject() || object->IsJSGlobalObject());
   } else {
-    DCHECK(context->IsFunctionContext());
+    DCHECK(context->IsFunctionContext() || context->IsEvalContext());
     object =
         isolate->factory()->NewJSObject(isolate->context_extension_function());
     context->set_extension(*object);
@@ -696,6 +696,16 @@ RUNTIME_FUNCTION(Runtime_NewFunctionContext) {
   return *isolate->factory()->NewFunctionContext(length, function);
 }
 
+RUNTIME_FUNCTION(Runtime_NewEvalContext) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+
+  CONVERT_ARG_HANDLE_CHECKED(JSFunction, function, 0);
+
+  DCHECK(function->context() == isolate->context());
+  int length = function->shared()->scope_info()->ContextLength();
+  return *isolate->factory()->NewEvalContext(length, function);
+}
 
 RUNTIME_FUNCTION(Runtime_PushWithContext) {
   HandleScope scope(isolate);