Don't re-read files when compute their analysis results.

pkg/analyzer/test/src/dart/analysis/driver_test.dart

 // Copyright (c) 2016, 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.test.driver;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 1383 matching lines @@
 
     {
       AnalysisResult result = await driver.getResult(a);
       expect(_getTopLevelVarType(result.unit, 'A1'), 'int');
       expect(_getTopLevelVarType(result.unit, 'A2'), 'int');
     }
 
     // Update "a" so that "A1" is now "double".
     // Get result for "a".
     //
-    // Even though we have not notified the driver about the change,
-    // we still get "double" for "A1", because getResult() re-read the content.
-    //
-    // We also get "double" for "A2", even though "A2" has the type from "b".
+    // We get "double" for "A2", even though "A2" has the type from "b".
     // That's because we check for "a" API signature consistency, and because
     // it has changed, we invalidated the dependency cache, relinked libraries
     // and recomputed types.
     provider.updateFile(
         a,
         r'''
 import 'b.dart';
 var A1 = 1.2;
 var A2 = B1;
 ''');
+    driver.changeFile(a);
+
     {
       AnalysisResult result = await driver.getResult(a);
       expect(_getTopLevelVarType(result.unit, 'A1'), 'double');
       expect(_getTopLevelVarType(result.unit, 'A2'), 'double');
     }
   }
 
   test_getResult_thenRemove() async {
     addTestFile('main() {}', priority: true);
 
@@ skipping 908 matching lines @@
    * Return the [provider] specific path for the given Posix [path].
    */
   String _p(String path) => provider.convertPath(path);
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }
 
 class _SourceMock extends TypedMock implements Source {}