Always update 'modificationTime' in _sourceChanged().

pkg/analyzer/test/src/context/context_test.dart

Index: pkg/analyzer/test/src/context/context_test.dart
diff --git a/pkg/analyzer/test/src/context/context_test.dart b/pkg/analyzer/test/src/context/context_test.dart
index a851f55013cb35dd0e1293a146ce75ee23a92449..5d151bf32aa6fff62ee9afcb6d01a4ffd6f6a30e 100644
--- a/pkg/analyzer/test/src/context/context_test.dart
+++ b/pkg/analyzer/test/src/context/context_test.dart
@@ -11,6 +11,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/dart/element/visitor.dart';
+import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/cancelable_future.dart';
@@ -279,6 +280,26 @@ int b = aa;''';
     });
   }
 
+  void test_applyChanges_changedSource_updateModificationTime() {
+    String path = '/test.dart';
+    File file = resourceProvider.newFile(path, 'var V = 1;');
+    Source source = file.createSource();
+    context.applyChanges(new ChangeSet()..addedSource(source));
+    // Analyze all.
+    _analyzeAll_assertFinished();
+    expect(context.analysisCache.getState(source, RESOLVED_UNIT),
+        CacheState.INVALID);
+    // Update the file and notify the context about the change.
+    resourceProvider.updateFile(path, 'var V = 2;');
+    context.applyChanges(new ChangeSet()..changedSource(source));
+    // The analysis results are invalidated.
+    // We have seen the new contents, so 'modificationTime' is also updated.
+    expect(context.analysisCache.getState(source, RESOLVED_UNIT),
+        CacheState.INVALID);
+    expect(
+        context.getCacheEntry(source).modificationTime, file.modificationStamp);
+  }
+
   void test_applyChanges_empty() {
     context.applyChanges(new ChangeSet());
     expect(context.performAnalysisTask().changeNotices, isNull);
@@ -2122,7 +2143,7 @@ library expectedToFindSemicolon
     if (context.analysisOptions.finerGrainedInvalidation) {
       expect(source.readCount, 7);
     } else {
-      expect(source.readCount, 4);
+      expect(source.readCount, 5);
     }
   }