Add an IsolateRunnable event to the service protocol. Improve service docs.

runtime/observatory/tests/service/isolate_lifecycle_test.dart

Index: runtime/observatory/tests/service/isolate_lifecycle_test.dart
diff --git a/runtime/observatory/tests/service/isolate_lifecycle_test.dart b/runtime/observatory/tests/service/isolate_lifecycle_test.dart
index 4495269b596301069b5d0ed4131e5c2be655d3d8..a3ad5400f1b7d34e07427188fb744294b0db8a1b 100644
--- a/runtime/observatory/tests/service/isolate_lifecycle_test.dart
+++ b/runtime/observatory/tests/service/isolate_lifecycle_test.dart
@@ -4,6 +4,7 @@
 // VMOptions=--error_on_bad_type --error_on_bad_override
 
 import 'dart:async';
+import 'dart:developer';
 import 'dart:isolate' as I;
 
 import 'package:observatory/service_io.dart';
@@ -18,7 +19,8 @@ final isolates = [];
 void spawnEntry(int i) {
 }
 
-Future before() async {
+Future during() async {
+  debugger();
   // Spawn spawnCount long lived isolates.
   for (var i = 0; i < spawnCount; i++) {
     var isolate = await I.Isolate.spawn(spawnEntry, i);
@@ -27,9 +29,6 @@ Future before() async {
   print('spawned all isolates');
 }
 
-Future during() async {
-}
-
 int numPaused(vm) {
   int paused = 0;
   for (var isolate in vm.isolates) {
@@ -42,20 +41,33 @@ int numPaused(vm) {
 
 var tests = [
   (VM vm) async {
+    expect(vm.isolates.length, 1);
+    await hasStoppedAtBreakpoint(vm.isolates[0]);
+  },
+
+  (VM vm) async {
     Completer completer = new Completer();
     var stream = await vm.getEventStream(VM.kIsolateStream);
-    if (vm.isolates.length < spawnCount + 1) {
-      var subscription;
-      subscription = stream.listen((ServiceEvent event) {
-        if (event.kind == ServiceEvent.kIsolateStart) {
-          if (vm.isolates.length == (spawnCount + 1)) {
-            subscription.cancel();
-            completer.complete(null);
-          }
-        }
-      });
-      await completer.future;
-    }
+    var subscription;
+    int startCount = 0;
+    int runnableCount = 0;
+    subscription = stream.listen((ServiceEvent event) {
+      if (event.kind == ServiceEvent.kIsolateStart) {
+        startCount++;
+      }
+      if (event.kind == ServiceEvent.kIsolateRunnable) {
+        runnableCount++;
+      }
+      if (runnableCount == spawnCount) {
+        subscription.cancel();
+        completer.complete(null);
+      }
+    });
+    expect(vm.isolates.length, 1);
+    vm.isolates[0].resume();
+    await completer.future;
+    expect(startCount, spawnCount);
+    expect(runnableCount, spawnCount);
     expect(vm.isolates.length, spawnCount + 1);
   },
 
@@ -124,6 +136,5 @@ var tests = [
 ];
 
 main(args) async => runVMTests(args, tests,
-                               testeeBefore: before,
                                testeeConcurrent: during,
                                pause_on_exit: true);