Fix some service protocol isolate lifecycle races

runtime/vm/service_event.h

 // Copyright (c) 2015, 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.
 
 #ifndef VM_SERVICE_EVENT_H_
 #define VM_SERVICE_EVENT_H_
 
 #include "vm/debugger.h"
 
 class DebuggerEvent;
@@ skipping 10 matching lines @@
     kIsolateExit,        // Isolate has exited
     kIsolateUpdate,      // Isolate identity information has changed
 
     kServiceExtensionAdded,  // A service extension was registered
 
     kPauseStart,         // --pause-isolates-on-start
     kPauseExit,          // --pause-isolates-on-exit
     kPauseBreakpoint,
     kPauseInterrupted,
     kPauseException,
+    kNone,               // isolate has not been made runnable yet.
     kResume,
     kBreakpointAdded,
     kBreakpointResolved,
     kBreakpointRemoved,
     kInspect,
     kDebuggerSettingsUpdate,
 
     kGC,
 
     kEmbedder,
@@ skipping 160 matching lines @@
   const uint8_t* bytes_;
   intptr_t bytes_length_;
   LogRecord log_record_;
   ExtensionEvent extension_event_;
   int64_t timestamp_;
 };
 
 }  // namespace dart
 
 #endif  // VM_SERVICE_EVENT_H_