observatory: optionally auto-refresh allocation profile page at each GC.

runtime/bin/vmservice/observatory/lib/src/elements/heap_profile.dart

Index: runtime/bin/vmservice/observatory/lib/src/elements/heap_profile.dart
===================================================================
--- runtime/bin/vmservice/observatory/lib/src/elements/heap_profile.dart	(revision 42293)
+++ runtime/bin/vmservice/observatory/lib/src/elements/heap_profile.dart	(working copy)
@@ -43,6 +43,8 @@
   var _classTableBody;
 
   @published ServiceMap profile;
+  @published bool autoRefresh = false;
+  var _subscription;
 
   @observable Isolate isolate;
 
@@ -91,8 +93,22 @@
     _oldPieChart = new Chart('PieChart',
         shadowRoot.querySelector('#oldPieChart'));
     _classTableBody = shadowRoot.querySelector('#classTableBody');
+    _subscription = app.vm.events.stream.where(
+        (event) => event.isolate == isolate).listen(_onEvent);
   }
 
+  @override
+  void detached() {
+    _subscription.cancel((){});
+    super.detached();
+  }
+  
+  void _onEvent(ServiceEvent event) {
+    if (autoRefresh && event.eventType == 'GC') {
+      refresh((){});
+    }
+  }
+  
   void _updatePieCharts() {
     assert(profile != null);
     _newPieDataTable.clearRows();