Add support for highlights notification

pkg/analyzer_plugin/lib/src/utilities/highlights/highlights.dart

+// 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 'package:analyzer/dart/analysis/results.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart'
+    hide AnalysisError;
+import 'package:analyzer_plugin/utilities/highlights/highlights.dart';
+
+/**
+ * A concrete implementation of [DartHighlightsRequest].
+ */
+class DartHighlightsRequestImpl implements DartHighlightsRequest {
+  @override
+  final ResourceProvider resourceProvider;
+
+  @override
+  final ResolveResult result;
+
+  /**
+   * Initialize a newly create request with the given data.
+   */
+  DartHighlightsRequestImpl(this.resourceProvider, this.result);
+
+  @override
+  String get path => result.path;
+}
+
+/**
+ * A concrete implementation of [HighlightsCollector].
+ */
+class HighlightsCollectorImpl implements HighlightsCollector {
+  /**
+   * The regions that have been collected.
+   */
+  List<HighlightRegion> regions = <HighlightRegion>[];
+
+  @override
+  void addRange(SourceRange range, HighlightRegionType type) {
+    regions.add(new HighlightRegion(type, range.offset, range.length));
+  }
+
+  @override
+  void addRegion(int offset, int length, HighlightRegionType type) {
+    regions.add(new HighlightRegion(type, offset, length));
+  }
+}