Add --verify-ir flag to dartk and test.py.

pkg/kernel/lib/ast.dart

Index: pkg/kernel/lib/ast.dart
diff --git a/pkg/kernel/lib/ast.dart b/pkg/kernel/lib/ast.dart
index 40a305ffae302b36811a9f499b808849372595a7..426dd87733e350a6cad22dcf32631d08198329c5 100644
--- a/pkg/kernel/lib/ast.dart
+++ b/pkg/kernel/lib/ast.dart
@@ -3012,6 +3012,7 @@ class VariableDeclaration extends Statement {
 
   static const int FlagFinal = 1 << 0; // Must match serialized bit positions.
   static const int FlagConst = 1 << 1;
+  static const int FlagInScope = 1 << 2; // Temporary flag used by verifier.
 
   bool get isFinal => flags & FlagFinal != 0;
   bool get isConst => flags & FlagConst != 0;