Remove the debugger_ field from Isolate in a PRODUCT build

runtime/vm/dart_entry.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/dart_entry.h"
 
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/debugger.h"
 #include "vm/object_store.h"
@@ skipping 543 matching lines @@
         zone, isolate_lib.PrivateName(Symbols::_handleMessage()));
     function = Resolver::ResolveStatic(isolate_lib, class_name, function_name,
                                        kTypeArgsLen, kNumArguments,
                                        Object::empty_array());
     ASSERT(!function.IsNull());
     isolate->object_store()->set_handle_message_function(function);
   }
   const Array& args = Array::Handle(zone, Array::New(kNumArguments));
   args.SetAt(0, handler);
   args.SetAt(1, message);
-  if (FLAG_support_debugger && isolate->debugger()->IsStepping()) {
+#if !defined(PRODUCT)
+  if (isolate->debugger()->IsStepping()) {
     // If the isolate is being debugged and the debugger was stepping
     // through code, enable single stepping so debugger will stop
     // at the first location the user is interested in.
     isolate->debugger()->SetResumeAction(Debugger::kStepInto);
   }
+#endif
   const Object& result =
       Object::Handle(zone, DartEntry::InvokeFunction(function, args));
   ASSERT(result.IsNull() || result.IsError());
   return result.raw();
 }
 
 RawObject* DartLibraryCalls::DrainMicrotaskQueue() {
   Zone* zone = Thread::Current()->zone();
   Library& isolate_lib = Library::Handle(zone, Library::IsolateLibrary());
   ASSERT(!isolate_lib.IsNull());
@@ skipping 19 matching lines @@
   const Array& args = Array::Handle(Array::New(kNumArguments));
   args.SetAt(0, map);
   args.SetAt(1, key);
   args.SetAt(2, value);
   const Object& result =
       Object::Handle(DartEntry::InvokeFunction(function, args));
   return result.raw();
 }
 
 }  // namespace dart