Add dart:developer.postEvent for posting events to the service protocol from Dart code

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 32786dd6df7604442d2811b2713604f074675bd8..ed4153bdd44dcb7e6a85af4a93dcb1ac9d88e927 100644
--- a/runtime/vm/service_event.h
+++ b/runtime/vm/service_event.h
@@ -41,6 +41,8 @@ class ServiceEvent {
 
     kLogging,
 
+    kExtension,
+
     kIllegal,
   };
 
@@ -55,6 +57,11 @@ class ServiceEvent {
     const Instance* stack_trace;
   };
 
+  struct ExtensionEvent {
+    const String* event_kind;
+    const String* event_data;
+  };
+
   ServiceEvent(Isolate* isolate, EventKind event_kind);
 
   explicit ServiceEvent(const DebuggerEvent* debugger_event);
@@ -162,6 +169,10 @@ class ServiceEvent {
     log_record_ = log_record;
   }
 
+  void set_extension_event(const ExtensionEvent& extension_event) {
+    extension_event_ = extension_event;
+  }
+
   int64_t timestamp() const {
     return timestamp_;
   }
@@ -186,6 +197,7 @@ class ServiceEvent {
   const uint8_t* bytes_;
   intptr_t bytes_length_;
   LogRecord log_record_;
+  ExtensionEvent extension_event_;
   int64_t timestamp_;
 };