Support BottomType in the VM Kernel reader

runtime/vm/kernel.cc

Index: runtime/vm/kernel.cc
diff --git a/runtime/vm/kernel.cc b/runtime/vm/kernel.cc
index c5e6700c90a0a40fa0680ca49e894a3db367ccdc..afebbc180bdec0fbeae25a9e6bd72d060d31a8b4 100644
--- a/runtime/vm/kernel.cc
+++ b/runtime/vm/kernel.cc
@@ -1168,6 +1168,17 @@ void VoidType::AcceptDartTypeVisitor(DartTypeVisitor* visitor) {
 void VoidType::VisitChildren(Visitor* visitor) {}
 
 
+BottomType::~BottomType() {}
+
+
+void BottomType::AcceptDartTypeVisitor(DartTypeVisitor* visitor) {
+  visitor->VisitBottomType(this);
+}
+
+
+void BottomType::VisitChildren(Visitor* visitor) {}
+
+
 InterfaceType::~InterfaceType() {}