Reduce service isolate startup time from ~80ms to ~30ms

runtime/vm/service.h

 // Copyright (c) 2013, 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_H_
 #define VM_SERVICE_H_
 
 #include "include/dart_api.h"
 
 #include "vm/allocation.h"
@@ skipping 20 matching lines @@
   static void HandleIsolateMessage(Isolate* isolate, const Array& message);
 
   static Isolate* GetServiceIsolate(void* callback_data);
   static bool SendIsolateStartupMessage();
   static bool SendIsolateShutdownMessage();
 
   static bool IsRunning() {
     return port_ != ILLEGAL_PORT;
   }
 
+  static void set_port(Dart_Port port) {
+    port_ = port;
+  }
+
   static void SetEventMask(uint32_t mask);
 
   // Is the service interested in debugger events?
   static bool NeedsDebuggerEvents() {
     return IsRunning() && ((event_mask_ & kEventFamilyDebugMask) != 0);
   }
   // Is the service interested in garbage collection events?
   static bool NeedsGCEvents() {
     return IsRunning() && ((event_mask_ & kEventFamilyGCMask) != 0);
   }
@@ skipping 43 matching lines @@
 
   static Isolate* service_isolate_;
   static Dart_LibraryTagHandler embedder_provided_handler_;
   static Dart_Port port_;
   static uint32_t event_mask_;
 };
 
 }  // namespace dart
 
 #endif  // VM_SERVICE_H_