Introduce "optimized_out" oddball marker for compilers.

src/compiler/js-graph.h

Index: src/compiler/js-graph.h
diff --git a/src/compiler/js-graph.h b/src/compiler/js-graph.h
index 5a25ed0697c8c335998920d82b7430d52ca950a2..06e80301649119ca60b00b057bdc9accc5ff4cf6 100644
--- a/src/compiler/js-graph.h
+++ b/src/compiler/js-graph.h
@@ -41,6 +41,7 @@ class JSGraph : public ZoneObject {
   // Canonicalized global constants.
   Node* CEntryStubConstant(int result_size);
   Node* EmptyFixedArrayConstant();
+  Node* OptimizedOutConstant();
   Node* UndefinedConstant();
   Node* TheHoleConstant();
   Node* TrueConstant();
@@ -136,6 +137,7 @@ class JSGraph : public ZoneObject {
   enum CachedNode {
     kCEntryStubConstant,
     kEmptyFixedArrayConstant,
+    kOptimizedOutConstant,
     kUndefinedConstant,
     kTheHoleConstant,
     kTrueConstant,