Add a task to the new task model for computing constant values.

pkg/analyzer/lib/src/task/general.dart

Index: pkg/analyzer/lib/src/task/general.dart
diff --git a/pkg/analyzer/lib/src/task/general.dart b/pkg/analyzer/lib/src/task/general.dart
index 69a808ee386bb7f1a377e5617f286c72f5284764..f49bb32d5f0f8f1168325a7ab2714d17154626b9 100644
--- a/pkg/analyzer/lib/src/task/general.dart
+++ b/pkg/analyzer/lib/src/task/general.dart
@@ -9,6 +9,7 @@ import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
+import 'package:analyzer/src/generated/element.dart';
 
 /**
  * A task that gets the contents of the source associated with an analysis
@@ -63,6 +64,25 @@ class GetContentTask extends SourceBasedAnalysisTask {
 }
 
 /**
+ * A base class for analysis tasks whose target is expected to be an element.
+ */
+abstract class ElementBasedAnalysisTask extends AnalysisTask {

[scheglov, 2015/05/08 18:46:08]

I'm not sure that this is a right place for this task.
Elements are probably too Dart specific.
Maybe move it to src/dart.dart ?

[Brian Wilkerson, 2015/05/08 19:22:38]

Agreed.

[Paul Berry, 2015/05/08 19:44:22]

Done.

+  /**
+   * Initialize a newly created task to perform analysis within the given
+   * [context] in order to produce results for the given [element].
+   */
+  ElementBasedAnalysisTask(AnalysisContext context, Element element)
+      : super(context, element);
+
+  @override
+  String get description {
+    Source source = target.source;
+    String sourceName = source == null ? '<unknown source>' : source.fullName;
+    return '${descriptor.name} for element $target in source $sourceName';
+  }
+}
+
+/**
  * A base class for analysis tasks whose target is expected to be a source.
  */
 abstract class SourceBasedAnalysisTask extends AnalysisTask {