Provide LINE_INFO using just UnlinkedUnit even though the full info is not available.

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/ast/ast.dart';
@@ skipping 702 matching lines @@
 
   @override
   Object/*=V*/ computeResult/*<V>*/(
       AnalysisTarget target, ResultDescriptor/*<V>*/ descriptor) {
     // Make sure we are not trying to invoke the task model in a reentrant
     // fashion.
     assert(!driver.isTaskRunning);
     CacheEntry entry = getCacheEntry(target);
     CacheState state = entry.getState(descriptor);
     if (state == CacheState.FLUSHED || state == CacheState.INVALID) {
+      // Check the result provider.
+      bool success = aboutToComputeResult(entry, descriptor);
+      if (success) {
+        return entry.getValue(descriptor);
+      }
+      // Compute the result.
       driver.computeResult(target, descriptor);
       entry = getCacheEntry(target);
     }
     state = entry.getState(descriptor);
     if (state == CacheState.ERROR) {
       throw new AnalysisException(
           'Cannot compute $descriptor for $target', entry.exception);
     }
     return entry.getValue(descriptor);
   }
@@ skipping 1496 matching lines @@
     }
     DartSdk sdk = factory.dartSdk;
     if (sdk == null) {
       throw new ArgumentError(
           "The source factory for an SDK analysis context must have a DartUriResolver");
     }
     return new AnalysisCache(
         <CachePartition>[AnalysisEngine.instance.partitionManager.forSdk(sdk)]);
   }
 }