Add folding support for plugins and update the main tutorial page

pkg/analyzer_plugin/test/plugin/folding_mixin_test.dart

Index: pkg/analyzer_plugin/test/plugin/folding_mixin_test.dart
diff --git a/pkg/analyzer_plugin/test/plugin/folding_mixin_test.dart b/pkg/analyzer_plugin/test/plugin/folding_mixin_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..bf6ede13e2cd6a51eab0b7f83b81a0e3c5f5ab57
--- /dev/null
+++ b/pkg/analyzer_plugin/test/plugin/folding_mixin_test.dart
@@ -0,0 +1,100 @@
+// Copyright (c) 2017, 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.
+
+import 'dart:async';
+
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/file_system/memory_file_system.dart';
+import 'package:analyzer/src/dart/analysis/driver.dart';
+import 'package:analyzer_plugin/plugin/folding_mixin.dart';
+import 'package:analyzer_plugin/protocol/protocol.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
+import 'package:analyzer_plugin/protocol/protocol_generated.dart';
+import 'package:analyzer_plugin/src/utilities/folding/folding.dart';
+import 'package:analyzer_plugin/utilities/folding/folding.dart';
+import 'package:path/src/context.dart';
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'mocks.dart';
+
+void main() {
+  defineReflectiveTests(FoldingMixinTest);
+}
+
+@reflectiveTest
+class FoldingMixinTest {
+  MemoryResourceProvider resourceProvider = new MemoryResourceProvider();
+
+  String packagePath1;
+  String filePath1;
+  ContextRoot contextRoot1;
+
+  MockChannel channel;
+  _TestServerPlugin plugin;
+
+  void setUp() {
+    Context pathContext = resourceProvider.pathContext;
+
+    packagePath1 = resourceProvider.convertPath('/package1');
+    filePath1 = pathContext.join(packagePath1, 'lib', 'test.dart');
+    resourceProvider.newFile(filePath1, '');
+    contextRoot1 = new ContextRoot(packagePath1, <String>[]);
+
+    channel = new MockChannel();
+    plugin = new _TestServerPlugin(resourceProvider);
+    plugin.start(channel);
+  }
+
+  test_sendFoldingNotification() async {
+    await plugin.handleAnalysisSetContextRoots(
+        new AnalysisSetContextRootsParams([contextRoot1]));
+
+    Completer<Null> notificationReceived = new Completer<Null>();
+    channel.listen(null, onNotification: (Notification notification) {
+      expect(notification, isNotNull);
+      AnalysisFoldingParams params =
+          new AnalysisFoldingParams.fromNotification(notification);
+      expect(params.file, filePath1);
+      List<FoldingRegion> regions = params.regions;
+      expect(regions, hasLength(7));
+      notificationReceived.complete();
+    });
+    await plugin.sendFoldingNotification(filePath1);
+    await notificationReceived.future;
+  }
+}
+
+class _TestFoldingContributor implements FoldingContributor {
+  int regionCount;
+
+  _TestFoldingContributor(this.regionCount);
+
+  @override
+  void computeFolding(FoldingRequest request, FoldingCollector collector) {
+    for (int i = 0; i < regionCount; i++) {
+      collector.addRegion(i * 20, 10, FoldingKind.COMMENT);
+    }
+  }
+}
+
+class _TestServerPlugin extends MockServerPlugin with FoldingMixin {
+  _TestServerPlugin(ResourceProvider resourceProvider)
+      : super(resourceProvider);
+
+  @override
+  List<FoldingContributor> getFoldingContributors(String path) {
+    return <FoldingContributor>[
+      new _TestFoldingContributor(3),
+      new _TestFoldingContributor(4)
+    ];
+  }
+
+  @override
+  Future<FoldingRequest> getFoldingRequest(String path) async {
+    AnalysisResult result = new AnalysisResult(
+        null, null, path, null, null, null, null, null, null, null, null);
+    return new DartFoldingRequestImpl(resourceProvider, result);
+  }
+}