DartWorkManager.getLibrariesContainingPart() should ask the ResultProvider for CONTAINING_LIBRARIES.

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

Index: pkg/analyzer/lib/src/task/dart_work_manager.dart
diff --git a/pkg/analyzer/lib/src/task/dart_work_manager.dart b/pkg/analyzer/lib/src/task/dart_work_manager.dart
index 6b2a96ecc7c2a8344667bf150b9b92ab4159e2e2..7de97e493c1fca73e9579a811f0e0288de004b87 100644
--- a/pkg/analyzer/lib/src/task/dart_work_manager.dart
+++ b/pkg/analyzer/lib/src/task/dart_work_manager.dart
@@ -202,6 +202,7 @@ class DartWorkManager implements WorkManager {
       }
     }
     List<Source> libraries = partLibrariesMap[part];
+    libraries ??= _getLibrariesContainingPartFromResultProvider(part);
     return libraries?.toList() ?? Source.EMPTY_LIST;
   }
 
@@ -355,6 +356,19 @@ class DartWorkManager implements WorkManager {
   }
 
   /**
+   * Ask the [context]'s result provider for [CONTAINING_LIBRARIES].
+   * Return the list of containing libraries, or `null` if unknown.
+   */
+  List<Source> _getLibrariesContainingPartFromResultProvider(Source part) {
+    CacheEntry cacheEntry = context.getCacheEntry(part);
+    bool knows = context.aboutToComputeResult(cacheEntry, CONTAINING_LIBRARIES);
+    if (knows) {
+      return cacheEntry.getValue(CONTAINING_LIBRARIES);
+    }
+    return null;
+  }
+
+  /**
    * Return the SDK [DartWorkManager] or this one.
    */
   DartWorkManager _getSdkDartWorkManager() {