Support tab completion of line:col in the debugger.

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

Index: runtime/observatory/lib/src/elements/script_inset.dart
diff --git a/runtime/observatory/lib/src/elements/script_inset.dart b/runtime/observatory/lib/src/elements/script_inset.dart
index d9d9b64d5b8763d93d9588a670413bcecb43b4ca..aad3a0b47007897131a990cdd4e7a1f0f1a7f35e 100644
--- a/runtime/observatory/lib/src/elements/script_inset.dart
+++ b/runtime/observatory/lib/src/elements/script_inset.dart
@@ -425,7 +425,12 @@ class ScriptInsetElement extends ObservatoryElement {
       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();
           }