Gather and report stats on the number of times flushed results are recomputed

pkg/analyzer/lib/src/context/cache.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.cache;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/dart/element/element.dart'
@@ skipping 268 matching lines @@
    * referenced by another source.
    */
   static int _EXPLICITLY_ADDED_FLAG = 0;
 
   /**
    * The next invalidation process identifier.
    */
   static int nextInvalidateId = 0;
 
   /**
+   * A table containing the number of times the value of a result descriptor was
+   * recomputed after having been flushed.
+   */
+  static final Map<ResultDescriptor, int> recomputedCounts =
+      new HashMap<ResultDescriptor, int>();
+
+  /**
    * The target this entry is about.
    */
   final AnalysisTarget target;
 
   /**
    * The partition that is responsible for this entry.
    */
   CachePartition _partition;
 
   /**
@@ skipping 224 matching lines @@
 //      print(
 //          'setValue $descriptor for $target value=$valueStr $dependedOn=$dependedOn');
 //    }
     _validateStateChange(descriptor, CacheState.VALID);
     TargetedResult thisResult = new TargetedResult(target, descriptor);
     if (_partition != null) {
       _partition.resultStored(thisResult, value);
     }
     ResultData data = getResultData(descriptor);
     _setDependedOnResults(data, thisResult, dependedOn);
+    if (data.state == CacheState.FLUSHED) {
+      int count = recomputedCounts[descriptor] ?? 0;
+      recomputedCounts[descriptor] = count + 1;
+    }
     data.state = CacheState.VALID;
     data.value = value ?? descriptor.defaultValue;
   }
 
   /**
    * If the result represented by the given [descriptor] is valid, set
    * it to the given [value], keep its dependency, and if [invalidateDependent]
    * invalidate all the dependent result.
    */
   void setValueIncremental(
@@ skipping 806 matching lines @@
   void resultAccessed(TargetedResult result) {}
 
   @override
   List<TargetedResult> resultStored(TargetedResult newResult, newValue) {
     return TargetedResult.EMPTY_LIST;
   }
 
   @override
   void targetRemoved(AnalysisTarget target) {}
 }