Add an analyzer method to flush resolved ASTs (for testing).

pkg/analyzer/test/generated/engine_test.dart

 // Copyright (c) 2014, 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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.engine_test;
 
 import 'dart:async';
@@ skipping 5800 matching lines @@
   void setContents(Source source, String contents) {
     fail("Unexpected invocation of setContents");
   }
   @override
   bool shouldErrorsBeAnalyzed(Source source, Object entry) {
     fail("Unexpected invocation of shouldErrorsBeAnalyzed");
     return false;
   }
 
   @override
+  void test_flushResolvedUnit(Source source) {
+    fail("Unexpected invocation of test_flushResolvedUnit");
+  }
+
+  @override
   bool validateCacheConsistency() {
     fail("Unexpected invocation of validateCacheConsistency");
     return false;
   }
 
   @override
   void visitCacheItems(void callback(Source source, SourceEntry dartEntry,
       DataDescriptor rowDesc, CacheState state)) {
     fail("Unexpected invocation of visitCacheItems");
   }
@@ skipping 801 matching lines @@
   @override
   bool exists() => true;
 }
 
 class _UniversalCachePartitionTest_test_setMaxCacheSize
     implements CacheRetentionPolicy {
   @override
   RetentionPriority getAstPriority(Source source, SourceEntry sourceEntry) =>
       RetentionPriority.LOW;
 }