Do nothing if the changed file is not known to the driver.

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 04e2fe95f8f4a6821bdc38fd4e756397203b6439..f14a6ca9d2cacc24e656929ed9ee4ef7e2450a16 100644
--- a/pkg/analyzer/test/src/dart/analysis/driver_test.dart
+++ b/pkg/analyzer/test/src/dart/analysis/driver_test.dart
@@ -362,6 +362,9 @@ var A = B;
     provider.updateFile(b, 'var B = 1.2;');
     driver.changeFile(b);
 
+    // "b" is not an added file, so it is not scheduled for analysis.
+    expect(driver.test.filesToAnalyze, isEmpty);
+
     // While "b" is not analyzed explicitly, it is analyzed implicitly.
     // The change causes "a" to be reanalyzed.
     await _waitForIdle();
@@ -372,6 +375,28 @@ var A = B;
     }
   }
 
+  test_changeFile_notUsed() async {
+    var a = _p('/test/lib/a.dart');
+    var b = _p('/other/b.dart');
+    provider.newFile(a, '');
+    provider.newFile(b, 'class B1 {}');
+
+    driver.addFile(a);
+
+    await _waitForIdle();
+    allResults.clear();
+
+    // Change "b" and notify.
+    // Nothing depends on "b", so nothing is analyzed.
+    provider.updateFile(b, 'class B2 {}');
+    driver.changeFile(b);
+    await _waitForIdle();
+    expect(allResults, isEmpty);
+
+    // This should not add "b" to the file state.
+    expect(driver.fsState.knownFilePaths, isNot(contains(b)));
+  }
+
   test_changeFile_selfConsistent() async {
     var a = _p('/test/lib/a.dart');
     var b = _p('/test/lib/b.dart');
@@ -455,6 +480,9 @@ var A2 = B1;
     // Notify the driver about the change.
     driver.changeFile(testFile);
 
+    // The file was added, so it is scheduled for analysis.
+    expect(driver.test.filesToAnalyze, contains(testFile));
+
     // We get a new result.
     {
       await _waitForIdle();