Redo "Steps towards making dart2js JS AST templates an indepentent library."

pkg/compiler/lib/src/io/source_information.dart

Index: pkg/compiler/lib/src/io/source_information.dart
diff --git a/pkg/compiler/lib/src/io/source_information.dart b/pkg/compiler/lib/src/io/source_information.dart
index 529426190dd8407ec9f5f9fc04d28faca10c2e75..c0e6e0a80d5f316b95036be267b685d710a6dc01 100644
--- a/pkg/compiler/lib/src/io/source_information.dart
+++ b/pkg/compiler/lib/src/io/source_information.dart
@@ -8,12 +8,13 @@ import '../dart2jslib.dart' show SourceSpan;
 import '../elements/elements.dart' show AstElement;
 import '../scanner/scannerlib.dart' show Token;
 import '../tree/tree.dart' show Node;
+import '../js/js.dart' show JavaScriptNodeSourceInformation;
 import 'code_output.dart';
 import 'source_file.dart';
 
 /// Interface for passing source information, for instance for use in source
 /// maps, through the backend.
-abstract class SourceInformation {
+abstract class SourceInformation extends JavaScriptNodeSourceInformation {
   SourceSpan get sourceSpan;
   void beginMapping(CodeOutput output);
   void endMapping(CodeOutput output);