Internally measure isolate uptime with monotonic time.

runtime/vm/service.cc

 // 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.
 
 #include "vm/service.h"
 
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 #include "platform/globals.h"
 
@@ skipping 3767 matching lines @@
 };
 
 
 void Service::PrintJSONForVM(JSONStream* js, bool ref) {
   JSONObject jsobj(js);
   jsobj.AddProperty("type", (ref ? "@VM" : "VM"));
   jsobj.AddProperty("name", GetVMName());
   if (ref) {
     return;
   }
-  Isolate* vm_isolate = Dart::vm_isolate();
   jsobj.AddProperty("architectureBits", static_cast<intptr_t>(kBitsPerWord));
   jsobj.AddProperty("targetCPU", CPU::Id());
   jsobj.AddProperty("hostCPU", HostCPUFeatures::hardware());
   jsobj.AddProperty("version", Version::String());
   jsobj.AddProperty("_profilerMode", FLAG_profile_vm ? "VM" : "Dart");
   jsobj.AddProperty64("pid", OS::ProcessId());
   jsobj.AddProperty64("_maxRSS", OS::MaxRSS());
-  int64_t start_time_millis =
-      (vm_isolate->start_time() / kMicrosecondsPerMillisecond);
-  jsobj.AddPropertyTimeMillis("startTime", start_time_millis);
+  jsobj.AddPropertyTimeMillis(
+      "startTime", OS::GetCurrentTimeMillis() - Dart::UptimeMillis());
   // Construct the isolate list.
   {
     JSONArray jsarr(&jsobj, "isolates");
     ServiceIsolateVisitor visitor(&jsarr);
     Isolate::VisitIsolates(&visitor);
   }
 }
 
 
 static bool GetVM(Thread* thread, JSONStream* js) {
@@ skipping 315 matching lines @@
     if (strcmp(method_name, method.name) == 0) {
       return &method;
     }
   }
   return NULL;
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart