Remove the debugger_ field from Isolate in a PRODUCT build

runtime/vm/exceptions.cc

Index: runtime/vm/exceptions.cc
diff --git a/runtime/vm/exceptions.cc b/runtime/vm/exceptions.cc
index 343373fa127adef6f5465ce76ed174207d028ef2..767be8c21d2215bbd7624c9ca40ca9c08b8bba6b 100644
--- a/runtime/vm/exceptions.cc
+++ b/runtime/vm/exceptions.cc
@@ -763,13 +763,13 @@ void Exceptions::Throw(Thread* thread, const Instance& exception) {
   // Do not notify debugger on stack overflow and out of memory exceptions.
   // The VM would crash when the debugger calls back into the VM to
   // get values of variables.
-  if (FLAG_support_debugger) {
-    Isolate* isolate = thread->isolate();
-    if (exception.raw() != isolate->object_store()->out_of_memory() &&
-        exception.raw() != isolate->object_store()->stack_overflow()) {
-      isolate->debugger()->PauseException(exception);
-    }
+#if !defined(PRODUCT)
+  Isolate* isolate = thread->isolate();
+  if (exception.raw() != isolate->object_store()->out_of_memory() &&
+      exception.raw() != isolate->object_store()->stack_overflow()) {
+    isolate->debugger()->PauseException(exception);
   }
+#endif
   // Null object is a valid exception object.
   ThrowExceptionHelper(thread, exception, StackTrace::Handle(thread->zone()),
                        false);