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

pkg/front_end/lib/src/base/source.dart

Index: pkg/front_end/lib/src/base/source.dart
diff --git a/pkg/front_end/lib/src/base/source.dart b/pkg/front_end/lib/src/base/source.dart
index e20a0345d88c31b7c34190bd59c75b21dd776755..0ed4747915f61d9d45bc041f720f635fe9cb7486 100644
--- a/pkg/front_end/lib/src/base/source.dart
+++ b/pkg/front_end/lib/src/base/source.dart
@@ -5,7 +5,6 @@
 import 'package:front_end/src/base/analysis_target.dart';
 import 'package:front_end/src/base/timestamped_data.dart';
 import 'package:front_end/src/base/uri_kind.dart';
-import 'package:source_span/source_span.dart' as source_span;
 
 /**
  * The interface `Source` defines the behavior of objects representing source code that can be
@@ -108,11 +107,6 @@ abstract class Source implements AnalysisTarget {
   Source get source => this;
 
   /**
-   * Return the [source_span.SourceFile] object corresponding to this source.
-   */
-  source_span.SourceFile get sourceFile;
-
-  /**
    * Return the URI from which this source was originally derived.
    *
    * @return the URI from which this source was originally derived