Dev compiler debugger related tweaks.

pkg/dev_compiler/lib/src/compiler/compiler.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:collection' show HashSet, Queue;
 import 'dart:convert' show JSON;
 import 'dart:io' show File;
 
 import 'package:analyzer/analyzer.dart'
     show AnalysisError, CompilationUnit, ErrorSeverity;
@@ skipping 584 matching lines @@
 
   for (int i = 0; i < list.length; i++) {
     list[i] = transformUri(list[i]);
   }
   map['file'] = transformUri(map['file']);
   return map;
 }
 
 /// Cleanup the dart_sdk source map.
 ///
-/// Strip out files that should not be included in the sdk sourcemap as they
-/// are implementation details that would just confuse users.
 /// Normalize sdk urls to use "dart:" for more understandable stack traces.
 Map cleanupSdkSourcemap(Map sourceMap) {
   var map = new Map.from(sourceMap);
-  map['sources'] = map['sources']
-      .map((url) => url.contains('/_internal/') ? null : url)
-      .toList();
+  map['sources'] = map['sources'].map((url) {
+    var urlPrefix = '../../../gen/patched_sdk/lib/';
+    if (!url.startsWith(urlPrefix)) throw new Error('Unexpected sdk url: $url');
+    return 'dart:${url.substring(urlPrefix.length)}';
+  }).toList();
   return map;
 }