Revert of [api] Clean up scopes and precheck instantiations cache

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index cbbfeb9d9e1fed44556ff2abd7b05deaf1bf7201..b2353aeffb84f8b781aa35360d0e3cca89702c35 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -3255,6 +3255,21 @@ bool StackLimitCheck::JsHasOverflowed(uintptr_t gap) const {
   return GetCurrentStackPosition() - gap < stack_guard->real_climit();
 }
 
+SaveContext::SaveContext(Isolate* isolate)
+    : isolate_(isolate), prev_(isolate->save_context()) {
+  if (isolate->context() != NULL) {
+    context_ = Handle<Context>(isolate->context());
+  }
+  isolate->set_save_context(this);
+
+  c_entry_fp_ = isolate->c_entry_fp(isolate->thread_local_top());
+}
+
+SaveContext::~SaveContext() {
+  isolate_->set_context(context_.is_null() ? NULL : *context_);
+  isolate_->set_save_context(prev_);
+}
+
 #ifdef DEBUG
 AssertNoContextChange::AssertNoContextChange(Isolate* isolate)
     : isolate_(isolate), context_(isolate->context(), isolate) {}