src: use BaseObjectPtr to store SNI context

Rather than relying on a link to the JS object, store a pointer to
the C++ object directly.

src/node_crypto.cc

@@ -2991,9 +2991,15 @@ void SSLWrap<Base>::CertCbDone(const FunctionCallbackInfo<Value>& args) {
     goto fire_cb;
 
   if (cons->HasInstance(ctx)) {
-    SecureContext* sc;
-    ASSIGN_OR_RETURN_UNWRAP(&sc, ctx.As<Object>());
-    w->sni_context_.Reset(env->isolate(), ctx);
+    SecureContext* sc = Unwrap<SecureContext>(ctx.As<Object>());
+    CHECK_NOT_NULL(sc);
+    // XXX: There is a method w->SetSNIContext(sc), and you might think that
+    // it makes sense to call that here and make setting w->sni_context_ part
+    // of it. In fact, that passes the test suite, although SetSNIContext()
+    // performs a lot more operations.
+    // If anybody is familiar enough with the TLS code to know whether it makes
+    // sense, please do so or document why it doesn't.
+    w->sni_context_ = BaseObjectPtr<SecureContext>(sc);
 
     int rv;
 

src/node_crypto.h

@@ -310,7 +310,7 @@ class SSLWrap {
   ClientHelloParser hello_parser_;
 
   v8::Global<v8::ArrayBufferView> ocsp_response_;
-  v8::Global<v8::Value> sni_context_;
+  BaseObjectPtr<SecureContext> sni_context_;
 
   friend class SecureContext;
 };

src/tls_wrap.cc

@@ -1065,10 +1065,9 @@ int TLSWrap::SelectSNIContextCallback(SSL* s, int* ad, void* arg) {
     return SSL_TLSEXT_ERR_NOACK;
   }
 
-  p->sni_context_.Reset(env->isolate(), ctx);
-
   SecureContext* sc = Unwrap<SecureContext>(ctx.As<Object>());
   CHECK_NOT_NULL(sc);
+  p->sni_context_ = BaseObjectPtr<SecureContext>(sc);
   p->SetSNIContext(sc);
   return SSL_TLSEXT_ERR_OK;
 }