Use SummarySdkAnalysisContext if the SDK has the analysis_summary file.

pkg/analyzer/lib/src/context/context.dart

 // Copyright (c) 2015, 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.
 
 library analyzer.src.context.context;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/element/element.dart';
@@ skipping 468 matching lines @@
   @override
   TypeSystem get typeSystem {
     if (_typeSystem == null) {
       _typeSystem = TypeSystem.create(this);
     }
     return _typeSystem;
   }
 
   @override
   bool aboutToComputeResult(CacheEntry entry, ResultDescriptor result) {
+    AnalysisTarget target = entry.target;
+    // TYPE_PROVIDER
+    if (target is AnalysisContextTarget && result == TYPE_PROVIDER) {
+      DartSdk dartSdk = sourceFactory.dartSdk;
+      if (dartSdk != null) {
+        AnalysisContext sdkContext = dartSdk.context;
+        if (!identical(sdkContext, this) &&
+            sdkContext is InternalAnalysisContext) {
+          return sdkContext.aboutToComputeResult(entry, result);
+        }
+      }
+    }
+    // A result for a Source.
+    Source source = target.source;
+    if (source != null) {
+      InternalAnalysisContext context = _cache.getContextFor(source);
+      if (!identical(context, this)) {
+        return context.aboutToComputeResult(entry, result);
+      }
+    }
     return false;
   }
 
   @override
   void addListener(AnalysisListener listener) {
     if (!_listeners.contains(listener)) {
       _listeners.add(listener);
     }
   }
 
@@ skipping 1510 matching lines @@
     }
     DartSdk sdk = factory.dartSdk;
     if (sdk == null) {
       throw new IllegalArgumentException(
           "The source factory for an SDK analysis context must have a DartUriResolver");
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }