move dart completion contributor instantiation

pkg/analysis_server/lib/src/provisional/completion/dart/completion_plugin.dart

Index: pkg/analysis_server/lib/src/provisional/completion/dart/completion_plugin.dart
diff --git a/pkg/analysis_server/lib/src/provisional/completion/dart/completion_plugin.dart b/pkg/analysis_server/lib/src/provisional/completion/dart/completion_plugin.dart
index 7a21bbb66137fd30b655964c0d14f6330265405b..99b53fe5683e24299da65e330fb2183570f71ad1 100644
--- a/pkg/analysis_server/lib/src/provisional/completion/dart/completion_plugin.dart
+++ b/pkg/analysis_server/lib/src/provisional/completion/dart/completion_plugin.dart
@@ -38,11 +38,11 @@ class DartCompletionPlugin implements Plugin {
   String get uniqueIdentifier => UNIQUE_IDENTIFIER;
 
   /**
-   * Return a list containing all of the Dart specific completion contributor
-   * factories that were contributed.
+   * Return a list containing all of the Dart specific completion contributors.
    */
-  List<DartCompletionContributorFactory> get contributorFactories =>
-      _contributorExtensionPoint.extensions;
+  List<DartCompletionContributorFactory> get contributors =>
+      _contributorExtensionPoint.extensions
+          .map((DartCompletionContributorFactory factory) => factory());

[scheglov, 2015/12/03 01:57:53]

Should we convert the result t List?
.toList();

I'm also a little bit worried that we call external code without usual
try/catch/log sequence.
But it might be fine for these presumably simple factories.

[danrubel, 2015/12/03 12:45:25]

Good question. I think for now I will switch the return type to Iterable, which
is all that callers should need.
Good point. We may add exception handling here and other places where we hand
off to unknown contributors, but for now CompletionDomainHander #
handleRequest(...) will capture the exception and report it to the client.

 
   @override
   void registerExtensionPoints(RegisterExtensionPoint registerExtensionPoint) {