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..7a66191ea1153b9d4de83bb7e063686e6f88fcf8 100644
--- a/runtime/vm/service.cc
+++ b/runtime/vm/service.cc
@@ -2965,7 +2965,7 @@ static bool Resume(Thread* thread, JSONStream* js) {
       isolate->debugger()->EnterSingleStepMode();
     }
     isolate->message_handler()->set_pause_on_start(false);
-    isolate->set_last_resume_timestamp();
+    isolate->Resume();
     if (Service::debug_stream.enabled()) {
       ServiceEvent event(isolate, ServiceEvent::kResume);
       Service::HandleEvent(&event);
@@ -2975,6 +2975,7 @@ static bool Resume(Thread* thread, JSONStream* js) {
   }
   if (isolate->message_handler()->paused_on_exit()) {
     isolate->message_handler()->set_pause_on_exit(false);
+    isolate->Resume();

[turnidge, 2016/02/03 21:33:37]

Does this send a resume event?  Do we want to suppress it?

[Cutch, 2016/02/03 23:04:05]

No it doesn't and I've actually renamed this to be "SetResumeRequest" so that it
matches it's sibling "GetAndClearResumeRequest".

     // We don't send a resume event because we will be exiting.
     PrintSuccess(js);
     return true;