Create default tasks if plugins are not being used

pkg/analyzer/test/src/context/abstract_context.dart

Index: pkg/analyzer/test/src/context/abstract_context.dart
diff --git a/pkg/analyzer/test/src/context/abstract_context.dart b/pkg/analyzer/test/src/context/abstract_context.dart
index 8e7b555c05e32b60eec9b289828af194cda5942c..568d52242cb48ff26f22a70b5290c288e8c3a879 100644
--- a/pkg/analyzer/test/src/context/abstract_context.dart
+++ b/pkg/analyzer/test/src/context/abstract_context.dart
@@ -85,13 +85,6 @@ class AbstractContextTest {
   }
 
   void setUp() {
-    // configure TaskManager
-    {
-      EnginePlugin plugin = AnalysisEngine.instance.enginePlugin;
-      if (plugin.taskExtensionPoint == null) {
-        extensionManager.processPlugins([plugin]);

[scheglov, 2015/05/19 21:09:25]

I this case the "extensionManager" field is not used at all and can be removed.

[Brian Wilkerson, 2015/05/19 21:12:08]

Done.

I also removed two unused imports.

-      }
-    }
     // prepare AnalysisContext
     sourceFactory = new SourceFactory(<UriResolver>[
       new DartUriResolver(sdk),