Implement type argument access and reification of runtime types.

pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart

Index: pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
diff --git a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
index 199d2d6f48c99bd33ca9b0bfa1fc8850faa9c317..c54ba4c845ae15b336fac228f3a6aaf64247bf78 100644
--- a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
+++ b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
@@ -659,6 +659,14 @@ class ParentVisitor extends RecursiveVisitor {
 
   processCreateBox(CreateBox node) {
   }
+
+  processReifyRuntimeType(ReifyRuntimeType node) {
+    node.value.parent = node;
+  }
+
+  processReadTypeVariable(ReadTypeVariable node) {
+    node.target.parent = node;
+  }
 }
 
 class _ReductionKind {