Set fileUri when creating library builders.

pkg/front_end/lib/src/fasta/target_implementation.dart

Index: pkg/front_end/lib/src/fasta/target_implementation.dart
diff --git a/pkg/front_end/lib/src/fasta/target_implementation.dart b/pkg/front_end/lib/src/fasta/target_implementation.dart
index b70e0f776090c4612bb60b345d20217d78142920..4400b123ad2e394be8d782f9c0179897d85098c9 100644
--- a/pkg/front_end/lib/src/fasta/target_implementation.dart
+++ b/pkg/front_end/lib/src/fasta/target_implementation.dart
@@ -26,7 +26,7 @@ abstract class TargetImplementation extends Target {
 
   /// Creates a [LibraryBuilder] corresponding to [uri], if one doesn't exist
   /// already.
-  LibraryBuilder createLibraryBuilder(Uri uri);
+  LibraryBuilder createLibraryBuilder(Uri uri, Uri fileUri);
 
   /// Add the classes extended or implemented directly by [cls] to [set].
   void addDirectSupertype(ClassBuilder cls, Set<ClassBuilder> set);