Revert of [turbofan] Add support for copy-on-write element stores.

src/compiler/simplified-operator.h

Index: src/compiler/simplified-operator.h
diff --git a/src/compiler/simplified-operator.h b/src/compiler/simplified-operator.h
index fac19f0882e6b02d2c52ec9a136577f6e5ebf9bd..d6b0af8b7755247b0cdd2586e3b0ed75aed1bf5a 100644
--- a/src/compiler/simplified-operator.h
+++ b/src/compiler/simplified-operator.h
@@ -147,8 +147,6 @@
   kFastTransition,  // simple transition, just updating the map.
   kSlowTransition   // full transition, round-trip to the runtime.
 };
-
-size_t hash_value(ElementsTransition);
 
 std::ostream& operator<<(std::ostream&, ElementsTransition);
 
@@ -313,9 +311,6 @@
   const Operator* ObjectIsString();
   const Operator* ObjectIsUndetectable();
 
-  // ensure-writable-fast-elements object, elements
-  const Operator* EnsureWritableFastElements();
-
   // transition-elements-kind object, from-map, to-map
   const Operator* TransitionElementsKind(ElementsTransition transition);