Connect analyzer's AnalysisError object to front_end's CompilationError.

pkg/analyzer/lib/src/source/source_resource.dart

Index: pkg/analyzer/lib/src/source/source_resource.dart
diff --git a/pkg/analyzer/lib/src/source/source_resource.dart b/pkg/analyzer/lib/src/source/source_resource.dart
index 63b906cb3c884cbfc89ea4bf170fce82acc9cb49..b7fb2d0b76f193f94760a9680ec9579ca9663c62 100644
--- a/pkg/analyzer/lib/src/source/source_resource.dart
+++ b/pkg/analyzer/lib/src/source/source_resource.dart
@@ -9,6 +9,7 @@ import 'dart:collection';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
+import 'package:source_span/source_span.dart' as source_span;
 
 /**
  * A function that can translate the contents of files on disk as they are read.
@@ -35,6 +36,8 @@ class FileSource extends Source {
    */
   static final Map<String, int> _idTable = new HashMap<String, int>();
 
+  source_span.SourceFile _sourceFile;
+
   /**
    * The URI from which this source was originally derived.
    */
@@ -119,6 +122,10 @@ class FileSource extends Source {
   String get shortName => file.shortName;
 
   @override
+  source_span.SourceFile get sourceFile => _sourceFile ??=
+      new source_span.SourceFile(file.readAsStringSync(), url: uri);
+
+  @override
   UriKind get uriKind => UriKind.fromScheme(uri.scheme);
 
   @override