Add TypeMirror.isSubtypeOf, TypeMirror.isAssignableTo, ClassMirror.isSubclassOf

sdk/lib/_internal/compiler/implementation/mirrors/dart2js_type_mirrors.dart

Index: sdk/lib/_internal/compiler/implementation/mirrors/dart2js_type_mirrors.dart
diff --git a/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_type_mirrors.dart b/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_type_mirrors.dart
index 8a5a41e33ceb4d163611228ce46590b3b8069f09..3652f00397dfb09474694e907ebc976321cd9e55 100644
--- a/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_type_mirrors.dart
+++ b/sdk/lib/_internal/compiler/implementation/mirrors/dart2js_type_mirrors.dart
@@ -54,6 +54,14 @@ abstract class Dart2JsTypeMirror
 
   bool get isDynamic => false;
 
+  bool isSubtypeOf(TypeMirror other) {
+    return mirrorSystem.compiler.types.isSubtype(this._type, other._type);
+  }
+
+  bool isAssignableTo(TypeMirror other) {
+    return mirrorSystem.compiler.types.isAssignable(this._type, other._type);
+  }
+
   String toString() => _type.toString();
 }
 
@@ -226,6 +234,18 @@ class Dart2JsClassDeclarationMirror
                                 InterfaceType type)
       : super(system, type);
 
+  bool isSubclassOf(ClassMirror other) {
+    if (other is! ClassMirror) throw new ArgumentError(other);
+    ClassMirror otherDeclaration = other.originalDeclaration;
+    ClassMirror c = this;
+    while (c != null) {
+      c = c.originalDeclaration;
+      if (c == otherDeclaration) return true;
+      c = c.superclass;
+    }
+    return false;
+  }
+
   String toString() => 'Mirror on class ${_type.name}';
 }