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 79234f847cbf57547006aaf96519b5210685a7ce..74146832b7177f7e7b954263afa941c30dbe6af7 100644
--- a/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
+++ b/pkg/compiler/lib/src/cps_ir/shrinking_reductions.dart
@@ -660,6 +660,14 @@ class ParentVisitor extends RecursiveVisitor {
 
   processCreateBox(CreateBox node) {
   }
+
+  processReifyRuntimeType(ReifyRuntimeType node) {
+    node.value.parent = node;
+  }
+
+  processReadTypeVariable(ReadTypeVariable node) {
+    node.target.parent = node;
+  }
 }
 
 class _ReductionKind {