Fix analysis.getNavigation with the new analysis 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 f14a6ca9d2cacc24e656929ed9ee4ef7e2450a16..0bc2d9a3c4fdaf18d0aea68f90024a33615d109c 100644
--- a/pkg/analyzer/test/src/dart/analysis/driver_test.dart
+++ b/pkg/analyzer/test/src/dart/analysis/driver_test.dart
@@ -598,6 +598,7 @@ main() {
     AnalysisResult result = await driver.getResult(testFile);
     expect(result.path, testFile);
     expect(result.uri.toString(), 'package:test/test.dart');
+    expect(result.exists, isTrue);
     expect(result.content, content);
     expect(result.contentHash, _md5(content));
     expect(result.unit, isNotNull);
@@ -633,6 +634,16 @@ main() {
     expect(result.errors, isEmpty);
   }
 
+  test_getResult_doesNotExist() async {
+    var a = _p('/test/lib/a.dart');
+
+    AnalysisResult result = await driver.getResult(a);
+    expect(result.path, a);
+    expect(result.uri.toString(), 'package:test/a.dart');
+    expect(result.exists, isFalse);
+    expect(result.content, '');
+  }
+
   test_getResult_errors() async {
     String content = 'main() { int vv; }';
     addTestFile(content, priority: true);