2nd attempt at adding streamListen/streamCancel to the service protocol.

runtime/vm/service_event.h

Index: runtime/vm/service_event.h
diff --git a/runtime/vm/service_event.h b/runtime/vm/service_event.h
index 0c90d006ffedc087ed985d55e7db6348de861e87..f835498a3ef36928581c9aa3c5608f7bdaee5108 100644
--- a/runtime/vm/service_event.h
+++ b/runtime/vm/service_event.h
@@ -24,13 +24,12 @@ class ServiceEvent {
     kPauseInterrupted,
     kPauseException,
     kResume,
-
     kBreakpointAdded,
     kBreakpointResolved,
     kBreakpointRemoved,
+    kInspect,
 
     kGC,
-    kInspect,
 
     kIllegal,
   };
@@ -50,6 +49,8 @@ class ServiceEvent {
 
   EventType type() const { return type_; }
 
+  const char* stream_id() const;
+
   Breakpoint* breakpoint() const {
     return breakpoint_;
   }