[Isolates] Pass current isolate address to the regexp native functions

src/interpreter-irregexp.cc

Index: src/interpreter-irregexp.cc
diff --git a/src/interpreter-irregexp.cc b/src/interpreter-irregexp.cc
index a60da93c9d46cf8e44a3dc0b30e70c5ad6179e6a..3e18c3657994ea1ab2afe1d5936c901df95a7e94 100644
--- a/src/interpreter-irregexp.cc
+++ b/src/interpreter-irregexp.cc
@@ -163,10 +163,9 @@ class BacktrackStack {
   }
 
   ~BacktrackStack() {
-    Isolate* isolate = Isolate::Current();
-    if (isolate->irregexp_interpreter_backtrack_stack_cache() == NULL) {
+    if (isolate_->irregexp_interpreter_backtrack_stack_cache() == NULL) {
       // The cache is empty. Keep this backtrack stack around.
-      isolate->set_irregexp_interpreter_backtrack_stack_cache(data_);
+      isolate_->set_irregexp_interpreter_backtrack_stack_cache(data_);
     } else {
       // A backtrack stack was already cached, just release this one.
       DeleteArray(data_);