feat(dart/analysis): Build DirectiveMetadata for LibrarySpecificUnit

initial commit for the dart analyzer task

modules_dart/analyzer_plugin/lib/tasks.dart

@@ -0,0 +1,9 @@
+library angular2.src.analysis.analyzer_plugin.tasks;
+
+import 'package:analyzer/src/generated/error.dart';
+import 'package:analyzer/task/model.dart';
+
+/// The analysis errors associated with a target.
+/// The value combines errors represented by multiple other results.
+final CompositeResultDescriptor<List<AnalysisError>> HTML_ERRORS =
+    new CompositeResultDescriptor<List<AnalysisError>>('ANGULAR_HTML_ERRORS');