Provide stdout and stderr output in the Observatory debugger.

runtime/vm/service.h

Index: runtime/vm/service.h
diff --git a/runtime/vm/service.h b/runtime/vm/service.h
index 85c607f309c1194a7da7488d709b6977fd67edd2..001a65d03050c34ae8f7cd56075f71217802b95e 100644
--- a/runtime/vm/service.h
+++ b/runtime/vm/service.h
@@ -73,7 +73,7 @@ class Service : public AllStatic {
   static bool NeedsEchoEvents() { return needs_echo_events_; }
   static bool NeedsGraphEvents() { return needs_graph_events_; }
 
-  static void ListenStream(const char* stream_id);
+  static bool ListenStream(const char* stream_id);
   static void CancelStream(const char* stream_id);
 
   static void HandleEvent(ServiceEvent* event);
@@ -88,10 +88,34 @@ class Service : public AllStatic {
       Dart_ServiceRequestCallback callback,
       void* user_data);
 
+  static void SetEmbedderStreamCallbacks(
+      Dart_ServiceStreamListenCallback listen_callback,
+      Dart_ServiceStreamCancelCallback cancel_callback);
+
   static void SendEchoEvent(Isolate* isolate, const char* text);
   static void SendGraphEvent(Isolate* isolate);
   static void SendInspectEvent(Isolate* isolate, const Object& inspectee);
 
+  static void SendEmbedderEvent(Isolate* isolate,
+                                const char* stream_id,
+                                const char* event_kind,
+                                const uint8_t* bytes,
+                                intptr_t bytes_len);
+
+  static Dart_ServiceStreamListenCallback stream_listen_callback() {
+    return stream_listen_callback_;
+  }
+  static Dart_ServiceStreamCancelCallback stream_cancel_callback() {
+    return stream_cancel_callback_;
+  }
+
+  // Well-known stream ids.
+  static const char* const kIsolateStreamId;
+  static const char* const kDebugStreamId;
+  static const char* const kGCStreamId;
+  static const char* const kEchoStreamId;
+  static const char* const kGraphStreamId;
+
  private:
   static void InvokeMethod(Isolate* isolate, const Array& message);
 
@@ -113,6 +137,8 @@ class Service : public AllStatic {
 
   static EmbedderServiceHandler* isolate_service_handler_head_;
   static EmbedderServiceHandler* root_service_handler_head_;
+  static Dart_ServiceStreamListenCallback stream_listen_callback_;
+  static Dart_ServiceStreamCancelCallback stream_cancel_callback_;
 
   static bool needs_isolate_events_;
   static bool needs_debug_events_;