Fix for resynthesizing libraries with invalid part URIs.

pkg/analyzer/test/src/summary/resynthesize_common.dart

Index: pkg/analyzer/test/src/summary/resynthesize_common.dart
diff --git a/pkg/analyzer/test/src/summary/resynthesize_common.dart b/pkg/analyzer/test/src/summary/resynthesize_common.dart
index 65259ba3d616bcd42267bf82c2d2ceb0d39e4fea..2879c7d143bb35028043ce26154a71d8dd079d74 100644
--- a/pkg/analyzer/test/src/summary/resynthesize_common.dart
+++ b/pkg/analyzer/test/src/summary/resynthesize_common.dart
@@ -4309,6 +4309,12 @@ void named({x: 1}) {}
     checkLibrary('library my.lib; part "a.dart"; part "b.dart";');
   }
 
+  test_parts_invalidUri() {
+    allowMissingFiles = true;
+    addSource('/foo/bar.dart', 'part of my.lib;');
+    checkLibrary('library my.lib; part "foo/";');
+  }
+
   test_propagated_type_refers_to_closure() {
     checkLibrary('''
 void f() {