Automatically step past async state-machine switch for 'anext'.

runtime/observatory/lib/src/elements/debugger.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library debugger_page_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'package:observatory/cli.dart';
@@ skipping 342 matching lines @@
   AsyncNextCommand(Debugger debugger) : super(debugger, 'anext', []) {
   }
 
   Future run(List<String> args) async {
     if (debugger.isolatePaused()) {
       var event = debugger.isolate.pauseEvent;
       if (event.asyncContinuation == null) {
         debugger.console.print("No async continuation at this location");
         return;
       }
-      var bpt = await
-          debugger.isolate.addBreakOnActivation(event.asyncContinuation);
-      return debugger.isolate.resume();
+      return debugger.isolate.asyncStepOver()[0];
     } else {
       debugger.console.print('The program is already running');
     }
   }
 
   String helpShort =
       'Step over await or yield';
 
   String helpLong =
       'Continue running the isolate until control returns to the current '
@@ skipping 614 matching lines @@
         new RefreshCommand(this),
     ]);
     _stdioPrinter = new _VMStreamPrinter(this);
   }
 
   VM get vm => page.app.vm;
 
   void updateIsolate(Isolate iso) {
     _isolate = iso;
     if (_isolate != null) {
-      if (exceptions != iso.exceptionsPauseInfo) {
+      if ((exceptions != iso.exceptionsPauseInfo) &&
+          (iso.exceptionsPauseInfo != null)) {
         exceptions = iso.exceptionsPauseInfo;
         console.print("Now pausing for $exceptions exceptions");
       }
 
       _isolate.reload().then((response) {
         // TODO(turnidge): Currently the debugger relies on all libs
         // being loaded.  Fix this.
         var pending = [];
         for (var lib in _isolate.libraries) {
           if (!lib.loaded) {
@@ skipping 115 matching lines @@
           console.print('Paused due to exception at '
                         '${script.name}:${line}:${col}');
           // This seems to be missing if we are paused-at-exception after
           // paused-at-isolate-exit. Maybe we shutdown part of the debugger too
           // soon?
           console.printRef(event.exception);
         } else {
           console.print('Paused at ${script.name}:${line}:${col}');
         }
         if (event.asyncContinuation != null) {
-          console.print("Paused in async function: 'astep' available");
+          console.print("Paused in async function: 'anext' available");
         }
       });
     }
   }
 
   Future _reportBreakpointEvent(ServiceEvent event) {
     var bpt = event.breakpoint;
     var verb = null;
     switch (event.kind) {
       case ServiceEvent.kBreakpointAdded:
@@ skipping 737 matching lines @@
       });
   }
 
   void focus() {
     $['textBox'].focus();
   }
 
   DebuggerInputElement.created() : super.created();
 }