Pass the sdk path to plugins

pkg/analysis_server/test/analysis_abstract.dart

Index: pkg/analysis_server/test/analysis_abstract.dart
diff --git a/pkg/analysis_server/test/analysis_abstract.dart b/pkg/analysis_server/test/analysis_abstract.dart
index 9b7a3640a8357997c691fa5396b56ffa0bfe5791..580dcf1b51f283d309326a9fa1dbf8f790750a52 100644
--- a/pkg/analysis_server/test/analysis_abstract.dart
+++ b/pkg/analysis_server/test/analysis_abstract.dart
@@ -305,6 +305,12 @@ class TestPluginManager implements PluginManager {
   }
 
   @override
+  String get sdkPath {
+    fail('Unexpected invocation of sdkPath');
+    return null;
+  }
+
+  @override
   Future<Null> addPluginToContextRoot(
       analyzer.ContextRoot contextRoot, String path) async {
     fail('Unexpected invocation of addPluginToContextRoot');