Add necessary support functions so that embedders can implemented pause on start and exit

runtime/vm/service.cc

Index: runtime/vm/service.cc
diff --git a/runtime/vm/service.cc b/runtime/vm/service.cc
index 24c159842a07daf34ab5c95b57c30f583b0993d6..595083f8ae0f427d6a09720575a3456d5d460f33 100644
--- a/runtime/vm/service.cc
+++ b/runtime/vm/service.cc
@@ -2958,14 +2958,14 @@ static const MethodParameter* resume_params[] = {
 static bool Resume(Thread* thread, JSONStream* js) {
   const char* step_param = js->LookupParam("step");
   Isolate* isolate = thread->isolate();
-  if (isolate->message_handler()->paused_on_start()) {
+  if (isolate->message_handler()->is_paused_on_start()) {
     // If the user is issuing a 'Over' or an 'Out' step, that is the
     // same as a regular resume request.
     if ((step_param != NULL) && (strcmp(step_param, "Into") == 0)) {
       isolate->debugger()->EnterSingleStepMode();
     }
-    isolate->message_handler()->set_pause_on_start(false);
-    isolate->set_last_resume_timestamp();
+    isolate->message_handler()->set_should_pause_on_start(false);
+    isolate->SetResumeRequest();
     if (Service::debug_stream.enabled()) {
       ServiceEvent event(isolate, ServiceEvent::kResume);
       Service::HandleEvent(&event);
@@ -2973,8 +2973,9 @@ static bool Resume(Thread* thread, JSONStream* js) {
     PrintSuccess(js);
     return true;
   }
-  if (isolate->message_handler()->paused_on_exit()) {
-    isolate->message_handler()->set_pause_on_exit(false);
+  if (isolate->message_handler()->is_paused_on_exit()) {
+    isolate->message_handler()->set_should_pause_on_exit(false);
+    isolate->SetResumeRequest();
     // We don't send a resume event because we will be exiting.
     PrintSuccess(js);
     return true;
@@ -2992,7 +2993,7 @@ static bool Resume(Thread* thread, JSONStream* js) {
         return true;
       }
     }
-    isolate->Resume();
+    isolate->SetResumeRequest();
     PrintSuccess(js);
     return true;
   }