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

pkg/analyzer/lib/error/error.dart

Index: pkg/analyzer/lib/error/error.dart
diff --git a/pkg/analyzer/lib/error/error.dart b/pkg/analyzer/lib/error/error.dart
index 8a4f9e8e21cedaee417f8fe1261684e40950cdc1..59eb1c4c1ebf1e49909119450709d0168294b31f 100644
--- a/pkg/analyzer/lib/error/error.dart
+++ b/pkg/analyzer/lib/error/error.dart
@@ -13,8 +13,10 @@ import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/source.dart';
+import 'package:front_end/compilation_error.dart';
 import 'package:front_end/src/base/errors.dart';
 import 'package:front_end/src/scanner/errors.dart';
+import 'package:source_span/src/span.dart';
 
 export 'package:front_end/src/base/errors.dart'
     show ErrorCode, ErrorSeverity, ErrorType;
@@ -642,7 +644,7 @@ ErrorCode errorCodeByUniqueName(String uniqueName) {
  *
  * See [AnalysisErrorListener].
  */
-class AnalysisError {
+class AnalysisError extends CompilationError {
   /**
    * An empty array of errors used when no errors are expected.
    */
@@ -750,6 +752,9 @@ class AnalysisError {
     return hashCode;
   }
 
+  @override
+  SourceSpan get span => source.sourceFile.span(offset, offset + length);
+
   /**
    * Return the message to be displayed for this error. The message should
    * indicate what is wrong and why it is wrong.