Restore UriReferencedElement and its uri/uriOffset/uriEnd properties.

pkg/analyzer/lib/src/task/dart.dart

Index: pkg/analyzer/lib/src/task/dart.dart
diff --git a/pkg/analyzer/lib/src/task/dart.dart b/pkg/analyzer/lib/src/task/dart.dart
index 75cd59d1fb5f5d68aed7211c00b876739e1d1bda..aab5d07f8d557f64588e0608a8482b59be22e7bb 100644
--- a/pkg/analyzer/lib/src/task/dart.dart
+++ b/pkg/analyzer/lib/src/task/dart.dart
@@ -1551,6 +1551,9 @@ class BuildLibraryElementTask extends SourceBasedAnalysisTask {
         CompilationUnit partUnit = partUnitMap[partSource];
         if (partUnit != null) {
           CompilationUnitElementImpl partElement = partUnit.element;
+          partElement.uriOffset = partUri.offset;
+          partElement.uriEnd = partUri.end;
+          partElement.uri = directive.uriContent;
           //
           // Validate that the part source is unique in the library.
           //