create new Dart specific completion contributor extension point

pkg/analysis_server/lib/src/plugin/server_plugin.dart

Index: pkg/analysis_server/lib/src/plugin/server_plugin.dart
diff --git a/pkg/analysis_server/lib/src/plugin/server_plugin.dart b/pkg/analysis_server/lib/src/plugin/server_plugin.dart
index c72ef9aa8ad438b00c9fbff5b02bb3caab5351f6..85cc38864c4ab5c8a6572f63aa4f03787b8a14ab 100644
--- a/pkg/analysis_server/lib/src/plugin/server_plugin.dart
+++ b/pkg/analysis_server/lib/src/plugin/server_plugin.dart
@@ -25,9 +25,12 @@ import 'package:analysis_server/src/domains/analysis/navigation_dart.dart';
 import 'package:analysis_server/src/domains/analysis/occurrences_dart.dart';
 import 'package:analysis_server/src/edit/edit_domain.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart';
+import 'package:analysis_server/src/provisional/completion/dart/completion.dart';
+import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/provisional/index/index.dart';
 import 'package:analysis_server/src/provisional/index/index_core.dart';
 import 'package:analysis_server/src/search/search_domain.dart';
+import 'package:analysis_server/src/services/completion/dart/completion_manager.dart';
 import 'package:analysis_server/src/services/correction/assist_internal.dart';
 import 'package:analysis_server/src/services/correction/fix_internal.dart';
 import 'package:analysis_server/src/services/index/index_contributor.dart';
@@ -67,6 +70,13 @@ class ServerPlugin implements Plugin {
 
   /**
    * The simple identifier of the extension point that allows plugins to
+   * register Dart specific completion contributor factories.
+   */
+  static const String DART_COMPLETION_CONTRIBUTOR_EXTENSION_POINT =
+      'dartCompletionContributor';
+
+  /**
+   * The simple identifier of the extension point that allows plugins to
    * register domains.
    */
   static const String DOMAIN_EXTENSION_POINT = 'domain';
@@ -126,6 +136,12 @@ class ServerPlugin implements Plugin {
   ExtensionPoint completionContributorExtensionPoint;
 
   /**
+   * The extension point that allows plugins to register Dart specific
+   * completion contributor factories.
+   */
+  ExtensionPoint dartCompletionContributorExtensionPoint;
+
+  /**
    * The extension point that allows plugins to register domains with the
    * server.
    */
@@ -193,6 +209,14 @@ class ServerPlugin implements Plugin {
       completionContributorExtensionPoint.extensions;
 
   /**
+   * Return a list containing all of the Dart specific completion contributor
+   * factories that were contributed.
+   */
+  List<
+      DartCompletionContributorFactory> get dartCompletionContributorFactories =>
+      dartCompletionContributorExtensionPoint.extensions;
+
+  /**
    * Return a list containing all of the fix contributors that were contributed.
    */
   List<FixContributor> get fixContributors =>
@@ -256,6 +280,9 @@ class ServerPlugin implements Plugin {
     completionContributorExtensionPoint = registerExtensionPoint(
         COMPLETION_CONTRIBUTOR_EXTENSION_POINT,
         _validateCompletionContributorExtension);
+    dartCompletionContributorExtensionPoint = registerExtensionPoint(
+        DART_COMPLETION_CONTRIBUTOR_EXTENSION_POINT,
+        _validateDartCompletionContributorExtension);
     domainExtensionPoint = registerExtensionPoint(
         DOMAIN_EXTENSION_POINT, _validateDomainExtension);
     fixContributorExtensionPoint = registerExtensionPoint(
@@ -291,7 +318,9 @@ class ServerPlugin implements Plugin {
     // Register completion contributors.
     //
     // TODO(brianwilkerson) Register the completion contributors.
-//    registerExtension(COMPLETION_CONTRIBUTOR_EXTENSION_POINT_ID, ???);
+    //registerExtension(COMPLETION_CONTRIBUTOR_EXTENSION_POINT_ID, ???);
+    registerExtension(DART_COMPLETION_CONTRIBUTOR_EXTENSION_POINT_ID,
+        defaultDartCompletionContributorFactory);
     //
     // Register analysis contributors.
     //
@@ -379,6 +408,18 @@ class ServerPlugin implements Plugin {
 
   /**
    * Validate the given extension by throwing an [ExtensionError] if it is not a
+   * valid Dart specific completion contributor.
+   */
+  void _validateDartCompletionContributorExtension(Object extension) {
+    if (extension is! DartCompletionContributorFactory) {
+      String id = dartCompletionContributorExtensionPoint.uniqueIdentifier;
+      throw new ExtensionError(
+          'Extensions to $id must be a DartCompletionContributorFactory');
+    }
+  }
+
+  /**
+   * Validate the given extension by throwing an [ExtensionError] if it is not a
    * valid domain.
    */
   void _validateDomainExtension(Object extension) {