Base JavaScript code position computation on JavaScript tracer.

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 18557558b989e54116bd6fb8fa8f4bbca4ad312e..0138b41701689e3dfc03c317f9bc5f31f1a1213b 100644
--- a/pkg/compiler/lib/src/io/source_information.dart
+++ b/pkg/compiler/lib/src/io/source_information.dart
@@ -21,6 +21,8 @@ bool useNewSourceInfo =
 /// Interface for passing source information, for instance for use in source
 /// maps, through the backend.
 abstract class SourceInformation extends JavaScriptNodeSourceInformation {
+  const SourceInformation();
+
   SourceSpan get sourceSpan;
 
   /// The source location associated with the start of the JS node.
@@ -47,6 +49,12 @@ class SourceInformationStrategy {
   SourceInformationBuilder createBuilderForContext(AstElement element) {
     return const SourceInformationBuilder();
   }
+
+  /// Generate [SourceInformation] marker for non-preamble code.
+  SourceInformation buildSourceMappedMarker() => null;
+
+  /// Called when compilation has completed.
+  void onComplete() {}
 }
 
 /// Interface for generating [SourceInformation].