Add DartSdk.getLinkedBundle() and use it in PubSummaryManager.

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

Index: pkg/analyzer/lib/src/generated/sdk.dart
diff --git a/pkg/analyzer/lib/src/generated/sdk.dart b/pkg/analyzer/lib/src/generated/sdk.dart
index e46b64438093fa0faa8e2dd48a7ad3c856554a45..7e86d8d965d7f70506c9bfe6da1045f51ab1f55b 100644
--- a/pkg/analyzer/lib/src/generated/sdk.dart
+++ b/pkg/analyzer/lib/src/generated/sdk.dart
@@ -12,6 +12,7 @@ import 'package:analyzer/src/generated/engine.dart'
     show AnalysisContext, AnalysisOptions, AnalysisOptionsImpl;
 import 'package:analyzer/src/generated/source.dart' show Source;
 import 'package:analyzer/src/generated/utilities_general.dart';
+import 'package:analyzer/src/summary/idl.dart' show PackageBundle;
 
 /**
  * A function used to create a new DartSdk with the given [options]. If the
@@ -78,6 +79,14 @@ abstract class DartSdk {
   Source fromFileUri(Uri uri);
 
   /**
+   * Return the linked [PackageBundle] for this SDK, if it can be provided, or
+   * `null` otherwise.
+   *
+   * This is a temporary API, don't use it.
+   */
+  PackageBundle getLinkedBundle();
+
+  /**
    * Return the library representing the library with the given 'dart:' [uri],
    * or `null` if the given URI does not denote a library in this SDK.
    */