Support tab completion of line:col in the debugger.

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 407 matching lines @@
   void _onDebugEvent(event) {
     if (script == null) {
       return;
     }
     switch (event.kind) {
       case ServiceEvent.kBreakpointAdded:
       case ServiceEvent.kBreakpointResolved:
       case ServiceEvent.kBreakpointRemoved:
         var loc = event.breakpoint.location;
         if (loc.script == script) {
-          int line = script.tokenToLine(loc.tokenPos);
+          int line;
+          if (loc.tokenPos != null) {
+            line = script.tokenToLine(loc.tokenPos);
+          } else {
+            line = script.tokenToLine(loc.line);
+          }
           if ((line >= _startLine) && (line <= _endLine)) {
             _updateTask.queue();
           }
         }
         break;
       default:
         // Ignore.
         break;
     }
   }
@@ skipping 574 matching lines @@
 @CustomTag('source-inset')
 class SourceInsetElement extends PolymerElement {
   SourceInsetElement.created() : super.created();
 
   @published SourceLocation location;
   @published String height = null;
   @published int currentPos;
   @published bool inDebuggerContext = false;
   @published ObservableList variables;
 }