Add a task for computing all constant values in a compilation unit.

pkg/analyzer/lib/src/generated/constant.dart

Index: pkg/analyzer/lib/src/generated/constant.dart
diff --git a/pkg/analyzer/lib/src/generated/constant.dart b/pkg/analyzer/lib/src/generated/constant.dart
index 1878062c4db6a6ec99f2e367e6b78c4d06bac4b0..1fb7b7f57346b2c02b031aabee39653bc6351e6a 100644
--- a/pkg/analyzer/lib/src/generated/constant.dart
+++ b/pkg/analyzer/lib/src/generated/constant.dart
@@ -900,6 +900,22 @@ class ConstantEvaluationTarget_Annotation implements ConstantEvaluationTarget {
 
   ConstantEvaluationTarget_Annotation(
       this.context, this.source, this.librarySource, this.annotation);
+
+  @override
+  int get hashCode => JenkinsSmiHash.hash4(context.hashCode, source.hashCode,
+      librarySource.hashCode, annotation.hashCode);
+
+  @override
+  bool operator ==(other) {
+    if (other is ConstantEvaluationTarget_Annotation) {
+      return this.context == other.context &&
+          this.source == other.source &&
+          this.librarySource == other.librarySource &&
+          this.annotation == other.annotation;
+    } else {
+      return false;
+    }
+  }
 }
 
 /**