Better reporting of ambiguous and "not found" commands in Obs debugger.

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:svg';
 import 'dart:html';
 import 'dart:math';
@@ skipping 1789 matching lines @@
   // TODO(turnidge): Implement real command line history.
   String lastCommand;
 
   Future run(String command) {
     if (command == '' && lastCommand != null) {
       command = lastCommand;
     }
     console.printBold('\$ $command');
     return cmd.runCommand(command).then((_) {
       lastCommand = command;
-    }).catchError((e, s) {
-      if (e is S.NetworkRpcException) {
+    }).catchError(
+      (e, s) {
         console.printRed('Unable to execute command because the connection '
-            'to the VM has been closed');
-      } else {
+                         'to the VM has been closed');
+      }, test: (e) => e is S.NetworkRpcException
+    ).catchError(
+      (e, s) {
+        console.printRed(e.toString());
+      }, test: (e) => e is CommandException
+    ).catchError(
+      (e, s) {
         if (s != null) {
           console.printRed('Internal error: $e\n$s');
         } else {
           console.printRed('Internal error: $e\n');
         }
       }
-    });
+    );
   }
 
   String historyPrev(String command) {
     return cmd.historyPrev(command);
   }
 
   String historyNext(String command) {
     return cmd.historyNext(command);
   }
 
@@ skipping 1425 matching lines @@
   ..setAttribute('height', '24')
   ..children = [
     new PathElement()
       ..setAttribute(
           'd',
           'M11 17h2v-6h-2v6zm1-15C6.48 2 2 6.48 2 12s4.48 10 '
           '10 10 10-4.48 10-10S17.52 2 12 2zm0 18c-4.41 '
           '0-8-3.59-8-8s3.59-8 8-8 8 3.59 8 8-3.59 8-8 8zM11 '
           '9h2V7h-2v2z')
   ];