[api] Clean up scopes and precheck instantiations cache

src/isolate-inl.h

Index: src/isolate-inl.h
diff --git a/src/isolate-inl.h b/src/isolate-inl.h
index c6a47a3f9f1b18ce818ab7978dfea34cae66f147..5c71d9188ec51da408f25b1334e0272abc3359e4 100644
--- a/src/isolate-inl.h
+++ b/src/isolate-inl.h
@@ -100,6 +100,20 @@ Isolate::ExceptionScope::~ExceptionScope() {
   isolate_->set_pending_exception(*pending_exception_);
 }
 
+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_);
+}
+
 #define NATIVE_CONTEXT_FIELD_ACCESSOR(index, type, name)     \
   Handle<type> Isolate::name() {                             \
     return Handle<type>(raw_native_context()->name(), this); \