Remove --experimental-classes flag and related dead code.

src/arm64/full-codegen-arm64.cc

Index: src/arm64/full-codegen-arm64.cc
diff --git a/src/arm64/full-codegen-arm64.cc b/src/arm64/full-codegen-arm64.cc
index ba9eb27f59b9a8b464c44efbde9be764be33d45d..dd47e0f1639d8d60957a4dbccc5673f1011cb09f 100644
--- a/src/arm64/full-codegen-arm64.cc
+++ b/src/arm64/full-codegen-arm64.cc
@@ -460,8 +460,7 @@ void FullCodeGenerator::EmitReturnSequence() {
       __ add(current_sp, current_sp, ip0);
       __ ret();
       int32_t arg_count = info_->scope()->num_parameters() + 1;
-      if (FLAG_experimental_classes &&
-          IsSubclassConstructor(info_->function()->kind())) {
+      if (IsSubclassConstructor(info_->function()->kind())) {
         arg_count++;
       }
       __ dc64(kXRegSize * arg_count);
@@ -2878,15 +2877,7 @@ void FullCodeGenerator::VisitCall(Call* expr) {
       }
     }
   } else if (call_type == Call::SUPER_CALL) {
-    if (FLAG_experimental_classes) {
-      EmitSuperConstructorCall(expr);
-    } else {
-      SuperReference* super_ref = callee->AsSuperReference();
-      EmitLoadSuperConstructor();
-      __ Push(result_register());
-      VisitForStackValue(super_ref->this_var());
-      EmitCall(expr, CallICState::METHOD);
-    }
+    EmitSuperConstructorCall(expr);
   } else {
     DCHECK(call_type == Call::OTHER_CALL);
     // Call to an arbitrary expression not handled specially above.