Rework error handling in the service protocol and in Observatory.

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

 // Copyright (c) 2013, 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 script_inset_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'observatory_element.dart';
 import 'service_ref.dart';
@@ skipping 441 matching lines @@
       e.classes.add("emptyBreakpoint");
       e.classes.add('noCopy');
       e.text = nbsp;
       return e;
     }
     e.text = 'B';
     update() {
       e.classes.clear();
       e.classes.add('noCopy');
 
-      if (busy) {
+      if (!line.possibleBpt) {
+        e.classes.add("emptyBreakpoint");
+        e.text = nbsp;
+      } else if (busy) {
         e.classes.add("busyBreakpoint");
       } else {
         if (line.breakpoints != null) {
           if (line.breakpointResolved) {
             e.classes.add("resolvedBreakpoint");
           } else {
             e.classes.add("unresolvedBreakpoint");
           }
         } else {
           e.classes.add("possibleBreakpoint");
         }
       }
     }
     line.changes.listen((_) => update());
     e.onClick.listen((event) {
       if (busy) {
         return;
       }
       busy = true;
       if (line.breakpoints == null) {
         // No breakpoint.  Add it.
         line.script.isolate.addBreakpoint(line.script, line.line).then((_) {
           busy = false;
           update();
+        }).catchError((e, st) {
+          bool suppressError = false;
+          if (e is ServerRpcException) {
+            ServerRpcException se = e;
+            suppressError = (se.code == ServerRpcException.kNoBreakAtLine);
+          }
+          if (!suppressError) {
+            return new Future.error(e, st);

[Cutch, 2015/05/13 17:50:09]

Maybe cleaner as:

if (e is ServiceRpcException && se.code == ...) {
  return new Future.value(null);
}

return new Future.error(e, st);

[turnidge, 2015/05/14 17:53:43]

Rewritten.

+          }
         });
       } else {
         // Existing breakpoint.  Remove it.
         List pending = [];
         for (var bpt in line.breakpoints) {
           pending.add(line.script.isolate.removeBreakpoint(bpt));
         }
         Future.wait(pending).then((_) {
           busy = false;
           update();
@@ skipping 59 matching lines @@
     }
 
     // So blank lines are included when copying script to the clipboard.
     e.append(span('\n'));
 
     return e;
   }
 
   ScriptInsetElement.created() : super.created();
 }