[Arguments] Fix a small bug and change some test expectations.

src/runtime.cc

 // Copyright 2010 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 7216 matching lines @@
       int index = argument_count - 1;
       while (index >= mapped_count) {
         // These go directly in the arguments array and have no
         // corresponding slot in the parameter map.
         arguments->set(index, *(parameters - index - 1));
         --index;
       }
 
       ScopeInfo<> scope_info(callee->shared()->scope_info());
       while (index >= 0) {
-        // Detect duplicate names.
+        // Detect duplicate names to the right in the parameter list.
         Handle<String> name = scope_info.parameter_name(index);
         int context_slot_count = scope_info.number_of_context_slots();
         bool duplicate = false;
-        for (int j = 0; j < index; ++j) {
+        for (int j = index + 1; j < parameter_count; ++j) {
           if (scope_info.parameter_name(j).is_identical_to(name)) {
             duplicate = true;
             break;
           }
         }
 
         if (duplicate) {
           // This goes directly in the arguments array with a hole in the
           // parameter map.
           arguments->set(index, *(parameters - index - 1));
@@ skipping 5051 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     COUNTERS->gc_last_resort_from_js()->Increment();
     HEAP->CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal