[turbofan] Some common operators are globally shared singletons.

src/compiler/operator.h

Index: src/compiler/operator.h
diff --git a/src/compiler/operator.h b/src/compiler/operator.h
index 8d17bc4d4d903e60925d6bfde6e7db5c57aadb07..5137806f1298b8dc58e1f400ef577620c83f0dc5 100644
--- a/src/compiler/operator.h
+++ b/src/compiler/operator.h
@@ -11,11 +11,6 @@
 
 namespace v8 {
 namespace internal {
-
-// Forward declarations.
-class ExternalReference;
-
-
 namespace compiler {
 
 // An operator represents description of the "computation" of a node in the
@@ -147,13 +142,6 @@ struct StaticParameterTraits {
   }
 };
 
-template <>
-struct StaticParameterTraits<ExternalReference> {
-  static OStream& PrintTo(OStream& os, ExternalReference reference);  // NOLINT
-  static int HashCode(ExternalReference reference);
-  static bool Equals(ExternalReference lhs, ExternalReference rhs);
-};
-
 // Specialization for static parameters of type {int}.
 template <>
 struct StaticParameterTraits<int> {