Improve VM connection flow in Observatory

runtime/observatory/lib/src/repositories/target.dart

Index: runtime/observatory/lib/src/repositories/target.dart
diff --git a/runtime/observatory/lib/src/repositories/target.dart b/runtime/observatory/lib/src/repositories/target.dart
index ec52128d96ea272456ef43d399590a9d9e8057fb..bb011600039f690113782b79570a3276326593bf 100644
--- a/runtime/observatory/lib/src/repositories/target.dart
+++ b/runtime/observatory/lib/src/repositories/target.dart
@@ -6,7 +6,8 @@ part of repositories;
 
 class TargetChangeEvent implements M.TargetChangeEvent {
   final TargetRepository repository;
-  TargetChangeEvent(this.repository);
+  final bool disconnected;
+  TargetChangeEvent(this.repository, [this.disconnected = false]);
 }
 
 class TargetRepository implements M.TargetRepository {
@@ -28,14 +29,18 @@ class TargetRepository implements M.TargetRepository {
 
   TargetRepository._(this._onChange, this.onChange) {
     _restore();
-    if (_list.isEmpty) {
-      _list.add(new SC.WebSocketVMTarget(_networkAddressOfDefaultTarget()));
+    // Add the default address if it doesn't already exist.
+    if (_find(_networkAddressOfDefaultTarget()) == null) {
+      add(_networkAddressOfDefaultTarget());
     }
-    current = _list.first;
+    // Set the current target to the default target.
+    current = _find(_networkAddressOfDefaultTarget());
   }
 
   void add(String address) {
-    if (_find(address) != null) return;
+    if (_find(address) != null) {
+      return;
+    }
     _list.insert(0, new SC.WebSocketVMTarget(address));
     _onChange.add(new TargetChangeEvent(this));
     _store();
@@ -45,13 +50,19 @@ class TargetRepository implements M.TargetRepository {
 
   void setCurrent(M.Target t) {
     SC.WebSocketVMTarget target = t as SC.WebSocketVMTarget;
-    if (!_list.contains(target)) return;
+    if (!_list.contains(target)) {
+      return;
+    }
     current = target;
     current.lastConnectionTime = new DateTime.now().millisecondsSinceEpoch;
     _onChange.add(new TargetChangeEvent(this));
     _store();
   }
 
+  void emitDisconnectEvent() {
+    _onChange.add(new TargetChangeEvent(this, true));
+  }
+
   void delete(o) {
     if (_list.remove(o)) {
       if (o == current) {