Create and test source mapping for invocations.

pkg/compiler/lib/src/source_file_provider.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 source_file_provider;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'dart:math' as math;
@@ skipping 85 matching lines @@
            sourceFiles[resourceUri] =
                new CachingUtf8BytesSourceFile(
                    resourceUri, resourceUri.toString(), result);
            return result;
          });
   }
 
   Future/*<List<int> | String>*/ call(Uri resourceUri);
 
   relativizeUri(Uri uri) => relativize(cwd, uri, isWindows);
+
+  SourceFile getSourceFile(Uri resourceUri) {
+    return sourceFiles[resourceUri];
+  }
 }
 
 class CompilerSourceFileProvider extends SourceFileProvider {
   Future<List<int>> call(Uri resourceUri) => readUtf8BytesFromUri(resourceUri);
 }
 
 class FormattingDiagnosticHandler {
   final SourceFileProvider provider;
   bool showWarnings = true;
   bool showHints = true;
@@ skipping 205 matching lines @@
   var onAdd, onClose;
 
   EventSinkWrapper(this.onAdd, this.onClose);
 
   void add(String data) => onAdd(data);
 
   void addError(error, [StackTrace stackTrace]) => throw error;
 
   void close() => onClose();
 }