Include uriToSource from dill-based libraries in output

pkg/front_end/lib/src/fasta/kernel/kernel_target.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
index 798e61b7ce04a51a4981d5b0588d6af8e029b6d5..0c4654b3072710de121a5057c5d284ea94dec84f 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_target.dart
@@ -371,8 +371,7 @@ class KernelTarget extends TargetImplementation {
         new Map<String, Source>.from(this.uriToSource);
 
     libraries.addAll(dillTarget.loader.libraries);
-    // TODO(scheglov) Should we also somehow update `uriToSource`?
-//    uriToSource.addAll(binary.uriToSource);
+    uriToSource.addAll(dillTarget.loader.uriToSource);
 
     // TODO(ahe): Remove this line. Kernel seems to generate a default line map
     // that used when there's no fileUri on an element. Instead, ensure all