Remove the debugger_ field from Isolate in a PRODUCT build

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index b33699429fef3dc04ca5fd0d2bd464a9cafdb199..ae6de71d32282a295d9a55874eddc1deddbffc13 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -5633,6 +5633,7 @@ DART_EXPORT Dart_Handle Dart_FinalizeLoading(bool complete_futures) {
 
   I->DoneFinalizing();
 
+#if !defined(PRODUCT)
   // Now that the newly loaded classes are finalized, notify the debugger
   // that new code has been loaded. If there are latent breakpoints in
   // the new code, the debugger convert them to unresolved source breakpoints.
@@ -5641,6 +5642,7 @@ DART_EXPORT Dart_Handle Dart_FinalizeLoading(bool complete_futures) {
   if (FLAG_support_debugger) {
     I->debugger()->NotifyDoneLoading();
   }
+#endif
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
   if (FLAG_enable_mirrors) {