Record information about parts of dependent libraries in summaries.

pkg/analyzer/lib/src/summary/summarize_elements.dart

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index 0aac780e54fb4fb313354d4bd19905dc7ced2520..0eac9105870c2b1f9a7e16479a27614c8999e83d 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -390,8 +390,11 @@ class _LibrarySerializer {
   int serializeDependency(LibraryElement dependentLibrary) {
     return dependencyMap.putIfAbsent(dependentLibrary, () {
       int index = dependencies.length;
+      List<String> parts = dependentLibrary.parts
+          .map((CompilationUnitElement e) => e.source.uri.toString())
+          .toList();
       dependencies.add(encodePrelinkedDependency(
-          uri: dependentLibrary.source.uri.toString()));
+          uri: dependentLibrary.source.uri.toString(), parts: parts));
       return index;
     });
   }