Revert "Immediately use the generic stub when storing into COW arrays"

src/ic.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1659 matching lines @@
 
   if (use_ic) {
     Handle<Code> stub = (strict_mode == kStrictMode)
         ? generic_stub_strict()
         : generic_stub();
     if (object->IsJSObject()) {
       Handle<JSObject> receiver = Handle<JSObject>::cast(object);
       if (receiver->elements()->map() ==
           isolate()->heap()->non_strict_arguments_elements_map()) {
         stub = non_strict_arguments_stub();
-      } else if (receiver->elements()->map() ==
-          isolate()->heap()->fixed_cow_array_map()) {
-        // Do nothing, just keep the generic stub.
       } else if (!force_generic) {
         if (key->IsSmi() && (target() != *non_strict_arguments_stub())) {
           StubKind stub_kind = STORE_NO_TRANSITION;
           if (receiver->GetElementsKind() == FAST_SMI_ONLY_ELEMENTS) {
             if (value->IsHeapNumber()) {
               stub_kind = STORE_TRANSITION_SMI_TO_DOUBLE;
             } else if (value->IsHeapObject()) {
               stub_kind = STORE_TRANSITION_SMI_TO_OBJECT;
             }
           } else if (receiver->GetElementsKind() == FAST_DOUBLE_ELEMENTS) {
@@ skipping 735 matching lines @@
 #undef ADDR
 };
 
 
 Address IC::AddressFromUtilityId(IC::UtilityId id) {
   return IC_utilities[id];
 }
 
 
 } }  // namespace v8::internal