Add AnalysisCache.flush() utility method.

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

Index: pkg/analyzer/lib/src/context/cache.dart
diff --git a/pkg/analyzer/lib/src/context/cache.dart b/pkg/analyzer/lib/src/context/cache.dart
index ae7961546a45a8f433ac8b2bf88b5b653f4f30fa..fa7fbadc89f83d4eefe032fbcde45e536ac9a83a 100644
--- a/pkg/analyzer/lib/src/context/cache.dart
+++ b/pkg/analyzer/lib/src/context/cache.dart
@@ -17,6 +17,12 @@ import 'package:analyzer/src/task/model.dart';
 import 'package:analyzer/task/model.dart';
 
 /**
+ * Return `true` if the [result] of the [target] should be flushed.
+ */
+typedef bool FlushResultFilter<V>(
+    AnalysisTarget target, ResultDescriptor<V> result);
+
+/**
  * Return `true` if the given [target] is a priority one.
  */
 typedef bool IsPriorityAnalysisTarget(AnalysisTarget target);
@@ -103,6 +109,15 @@ class AnalysisCache {
   }
 
   /**
+   * Flush results that satisfy the given [filter].
+   */
+  void flush(FlushResultFilter filter) {
+    for (CachePartition partition in _partitions) {
+      partition.flush(filter);
+    }
+  }
+
+  /**
    * Return the entry associated with the given [target].
    */
   CacheEntry get(AnalysisTarget target) {
@@ -392,6 +407,17 @@ class CacheEntry {
   }
 
   /**
+   * Flush results that satisfy the given [filter].
+   */
+  void flush(FlushResultFilter filter) {
+    _resultMap.forEach((ResultDescriptor result, ResultData data) {
+      if (filter(target, result)) {
+        data.flush();
+      }
+    });
+  }
+
+  /**
    * Return the result data associated with the [descriptor], creating one if it
    * isn't there.
    */
@@ -998,6 +1024,15 @@ abstract class CachePartition {
   }
 
   /**
+   * Flush results that satisfy the given [filter].
+   */
+  void flush(FlushResultFilter filter) {
+    for (CacheEntry entry in entryMap.values) {
+      entry.flush(filter);
+    }
+  }
+
+  /**
    * Return the entry associated with the given [target].
    */
   CacheEntry get(AnalysisTarget target) => entryMap[target];