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

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index 43d308eb52fae79ee2c5bb23c9905d7760d5a1c4..74a28bc58569af43a88350f43233f1ef4ae6d949 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -1365,6 +1365,74 @@ DART_EXPORT void Dart_ThreadEnableProfiling() {
 }
 
 
+DART_EXPORT bool Dart_ShouldPauseOnStart() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->pause_on_start();
+}
+
+
+DART_EXPORT void Dart_SetShouldPauseOnStart(bool v) {

[turnidge, 2016/02/03 21:33:36]

v -> value or perhaps should_pause.

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

Done.

+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  isolate->set_pause_isolates_flags_overridden(true);
+  return isolate->message_handler()->set_pause_on_start(v);
+}
+
+
+DART_EXPORT bool Dart_IsPausedOnStart() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->paused_on_start();
+}
+
+
+DART_EXPORT void Dart_SetPausedOnStart(bool v) {

[turnidge, 2016/02/03 21:33:36]

v -> value or paused, here and below.

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

Done.

+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  if (isolate->message_handler()->paused_on_start() != v) {
+    isolate->message_handler()->PausedOnStart(v);
+    if (v) {
+      isolate->message_handler()->NotifyPauseOnStart();
+    }
+  }

[turnidge, 2016/02/03 21:33:36]

As discussed offline, consider making a single api entry point
(SetPausedOnStart) instead of the current two public ones (PausedOnStart,
NotifyPauseOnStart).

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

Done.

+}
+
+
+DART_EXPORT bool Dart_ShouldPauseOnExit() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->pause_on_exit();
+}
+
+
+DART_EXPORT void Dart_SetShouldPauseOnExit(bool v) {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  isolate->set_pause_isolates_flags_overridden(true);
+  return isolate->message_handler()->set_pause_on_exit(v);
+}
+
+
+DART_EXPORT bool Dart_IsPausedOnExit() {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  return isolate->message_handler()->paused_on_exit();
+}
+
+
+DART_EXPORT void Dart_SetPausedOnExit(bool v) {
+  Isolate* isolate = Isolate::Current();
+  CHECK_ISOLATE(isolate);
+  if (isolate->message_handler()->paused_on_exit() != v) {
+    isolate->message_handler()->PausedOnExit(v);
+    if (v) {
+      isolate->message_handler()->NotifyPauseOnExit();
+    }
+  }
+}
+
+
 DART_EXPORT void Dart_ExitIsolate() {
   Thread* T = Thread::Current();
   CHECK_ISOLATE(T->isolate());
@@ -1579,6 +1647,22 @@ DART_EXPORT Dart_Handle Dart_HandleMessage() {
 }
 
 
+DART_EXPORT Dart_Handle Dart_HandleMessages() {
+  Thread* T = Thread::Current();
+  Isolate* I = T->isolate();
+  CHECK_API_SCOPE(T);
+  CHECK_CALLBACK_STATE(T);
+  API_TIMELINE_BEGIN_END;
+  TransitionNativeToVM transition(T);
+  if (I->message_handler()->HandleNormalMessages() != MessageHandler::kOK) {
+    Dart_Handle error = Api::NewHandle(T, I->object_store()->sticky_error());
+    I->object_store()->clear_sticky_error();
+    return error;
+  }
+  return Api::Success();
+}
+
+
 DART_EXPORT bool Dart_HandleServiceMessages() {
   Thread* T = Thread::Current();
   Isolate* I = T->isolate();