[analyzer] Make a pubic URI for clients to import TimestampedData.

The `TimestampedData` class is already exposed through the analyzer
API as a result of its use in the public `Source` class; this change
merely allows clients to refer to it directly without importing from
`package:analyzer/src`.

Making this change will allow an import of `package:analyzer/src` to
be removed from dartdoc.

Change-Id: I4d28662854513ba0098ef1f5279cb7cb276e832b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/442163
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>

pkg/analyzer/api.txt

diff --git a/pkg/analyzer/api.txt b/pkg/analyzer/api.txt
index 9f356c6..accb8f7 100644
--- a/pkg/analyzer/api.txt
+++ b/pkg/analyzer/api.txt
@@ -5199,6 +5199,11 @@
     intersects (method: bool Function(SourceRange?))
     startsIn (method: bool Function(SourceRange))
     toString (method: String Function())
+package:analyzer/source/timestamped_data.dart:
+  TimestampedData (class<E> extends Object):
+    new (constructor: TimestampedData<E> Function(int, E))
+    data (getter: E)
+    modificationTime (getter: int)
 package:analyzer/src/dart/analysis/experiments_impl.dart:
   ExperimentalFeature (class extends Object implements Feature):
     new (constructor: ExperimentalFeature Function({List<String> channels, required String documentation, required String enableString, required Version? experimentalReleaseVersion, required int index, required bool isEnabledByDefault, required bool isExpired, required Version? releaseVersion}))
@@ -5227,11 +5232,6 @@
     definedNames2 (getter: Map<String, Element>)
     get2 (method: Element? Function(String))
     getPrefixed2 (method: Element? Function(String, String))
-package:analyzer/src/generated/timestamped_data.dart:
-  TimestampedData (class<E> extends Object):
-    new (constructor: TimestampedData<E> Function(int, E))
-    data (getter: E)
-    modificationTime (getter: int)
 package:analyzer/src/lint/config.dart:
   RuleConfig (non-public)
 package:analyzer/src/workspace/workspace.dart:

pkg/analyzer/lib/source/timestamped_data.dart

diff --git a/pkg/analyzer/lib/source/timestamped_data.dart b/pkg/analyzer/lib/source/timestamped_data.dart
new file mode 100644
index 0000000..eaaec7d
--- /dev/null
+++ b/pkg/analyzer/lib/source/timestamped_data.dart
@@ -0,0 +1,16 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Analysis data for which we have a modification time.
+class TimestampedData<E> {
+  /// The modification time of the source from which the data was created.
+  final int modificationTime;
+
+  /// The data that was created from the source.
+  final E data;
+
+  /// Initialize a newly created holder to associate the given [data] with the
+  /// given [modificationTime].
+  TimestampedData(this.modificationTime, this.data);
+}

pkg/analyzer/lib/src/generated/timestamped_data.dart

diff --git a/pkg/analyzer/lib/src/generated/timestamped_data.dart b/pkg/analyzer/lib/src/generated/timestamped_data.dart
index 5499be0..3dec324 100644
--- a/pkg/analyzer/lib/src/generated/timestamped_data.dart
+++ b/pkg/analyzer/lib/src/generated/timestamped_data.dart
@@ -2,18 +2,10 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'package:_fe_analyzer_shared/src/base/analyzer_public_api.dart';
+// This export is needed because package `dartdoc` imports the `TimestampedData`
+// class from here.
+//
+// TODO(paulberry): update dartdoc's import, so that this library can be
+// deprecated and eventually removed.
 
-/// Analysis data for which we have a modification time.
-@AnalyzerPublicApi(message: 'exposed by Source.contents')
-class TimestampedData<E> {
-  /// The modification time of the source from which the data was created.
-  final int modificationTime;
-
-  /// The data that was created from the source.
-  final E data;
-
-  /// Initialize a newly created holder to associate the given [data] with the
-  /// given [modificationTime].
-  TimestampedData(this.modificationTime, this.data);
-}
+export 'package:analyzer/source/timestamped_data.dart' show TimestampedData;