Observatory improvements for exploring compiled code.

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 421 matching lines @@
   }
 
   void computeAnnotations() {
     _startLine = (startPos != null
                   ? script.tokenToLine(startPos)
                   : 1 + script.lineOffset);
     _currentLine = (currentPos != null
                     ? script.tokenToLine(currentPos)
                     : null);
     _currentCol = (currentPos != null
-                   ? (script.tokenToCol(currentPos) - 1)  // make this 0-based.
+                   ? (script.tokenToCol(currentPos))
                    : null);
+    if (_currentCol != null) {
+      _currentCol--;  // make this 0-based.
+    }
+
     _endLine = (endPos != null
                 ? script.tokenToLine(endPos)
                 : script.lines.length + script.lineOffset);
 
     annotations.clear();
 
     addCurrentExecutionAnnotation();
 
     if (!inDebuggerContext && script.library != null) {
       loadDeclarationsOfLibrary(script.library);
@@ skipping 103 matching lines @@
                                                       variable['value']));
         }
       }
     }
   }
 
   Element linesTable() {
     var table = new DivElement();
     table.classes.add("sourceTable");
 
+    if (_startLine == null || _endLine == null) {
+      return table;
+    }
+
     annotationsCursor = 0;
 
     int blankLineCount = 0;
     for (int i = _startLine; i <= _endLine; i++) {
       var line = script.getLine(i);
       if (line.isBlank) {
         // Try to introduce elipses if there are 4 or more contiguous
         // blank lines.
         blankLineCount++;
       } else {
@@ skipping 184 matching lines @@
 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;
 }