Use regular map-checks to guard string-length loading.

src/stub-cache.h

 // 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 554 matching lines @@
 
   static void GenerateLoadArrayLength(MacroAssembler* masm,
                                       Register receiver,
                                       Register scratch,
                                       Label* miss_label);
 
   static void GenerateLoadStringLength(MacroAssembler* masm,
                                        Register receiver,
                                        Register scratch1,
                                        Register scratch2,
-                                       Label* miss_label,
-                                       bool support_wrappers);
+                                       Label* miss_label);
 
   static void GenerateLoadFunctionPrototype(MacroAssembler* masm,
                                             Register receiver,
                                             Register scratch1,
                                             Register scratch2,
                                             Label* miss_label);
 
   static void TailCallBuiltin(MacroAssembler* masm, Builtins::Name name);
 
   // Generates code that verifies that the property holder has not changed
@@ skipping 624 matching lines @@
   Handle<JSFunction> constant_function_;
   bool is_simple_api_call_;
   Handle<FunctionTemplateInfo> expected_receiver_type_;
   Handle<CallHandlerInfo> api_call_info_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_STUB_CACHE_H_