Don't sent errors for general files if the file has the same signature.

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

Index: pkg/analyzer/test/src/dart/analysis/driver_test.dart
diff --git a/pkg/analyzer/test/src/dart/analysis/driver_test.dart b/pkg/analyzer/test/src/dart/analysis/driver_test.dart
index 7fcf61d0c0a8c2c4a1a8748a420da85e2c235425..7bd4dcec793f05dacf52c28ee11f55b33fe7ca3a 100644
--- a/pkg/analyzer/test/src/dart/analysis/driver_test.dart
+++ b/pkg/analyzer/test/src/dart/analysis/driver_test.dart
@@ -2213,6 +2213,28 @@ var A = B;
     expect(result.errors, hasLength(0));
   }
 
+  test_results_skipNotAffected() async {
+    var a = _p('/test/lib/a.dart');
+    var b = _p('/test/lib/b.dart');
+    provider.newFile(a, 'class A {}');
+    provider.newFile(b, 'class B {}');
+
+    driver.addFile(a);
+    driver.addFile(b);
+    await scheduler.waitForIdle();
+
+    expect(allResults, hasLength(2));
+    allResults.clear();
+
+    // Update a.dart and notify.
+    provider.updateFile(a, 'class A2 {}');
+    driver.changeFile(a);
+
+    // Only result for a.dart should be produced, b.dart is not affected.
+    await scheduler.waitForIdle();
+    expect(allResults, hasLength(1));
+  }
+
   test_results_status() async {
     addTestFile('int f() => 42;');
     await scheduler.waitForIdle();