Fix analysis.getNavigation with the new analysis driver.

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 580 matching lines @@
     expect(fooId, isNonNegative);
   }
 
   test_getResult() async {
     String content = 'int f() => 42;';
     addTestFile(content, priority: true);
 
     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);
     expect(result.errors, hasLength(0));
 
     var f = result.unit.declarations[0] as FunctionDeclaration;
     expect(f.name.staticType.toString(), '() → int');
     expect(f.returnType.type.toString(), 'int');
 
     // The same result is also received through the stream.
@@ skipping 15 matching lines @@
 }
 ''');
     driver.addFile(a);
     driver.addFile(b);
     await _waitForIdle();
 
     AnalysisResult result = await driver.getResult(b);
     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);
 
     AnalysisResult result = await driver.getResult(testFile);
     expect(result.path, testFile);
     expect(result.errors, hasLength(1));
     {
       AnalysisError error = result.errors[0];
       expect(error.offset, 13);
@@ skipping 1033 matching lines @@
   String _p(String path) => provider.convertPath(path);
 
   Future<Null> _waitForIdle() async {
     await idleStatusMonitor.signal;
   }
 
   static String _md5(String content) {
     return hex.encode(md5.convert(UTF8.encode(content)).bytes);
   }
 }