Minor change to for-in...

src/arm/full-codegen-arm.cc

 // Copyright 2009 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 938 matching lines @@
   __ ldr(r2, MemOperand(sp, 3 * kPointerSize));
 
   // Check if the expected map still matches that of the enumerable.
   // If not, we have to filter the key.
   Label update_each;
   __ ldr(r1, MemOperand(sp, 4 * kPointerSize));
   __ ldr(r4, FieldMemOperand(r1, HeapObject::kMapOffset));
   __ cmp(r4, Operand(r2));
   __ b(eq, &update_each);
 
-  // Convert the entry to a string or null if it isn't a property
-  // anymore. If the property has been removed while iterating, we
+  // Convert the entry to a string or (smi) 0 if it isn't a property
+  // any more. If the property has been removed while iterating, we
   // just skip it.
   __ push(r1);  // Enumerable.
   __ push(r3);  // Current entry.
   __ InvokeBuiltin(Builtins::FILTER_KEY, CALL_JS);
-  __ mov(r3, Operand(r0));
-  __ LoadRoot(ip, Heap::kNullValueRootIndex);
-  __ cmp(r3, ip);
+  __ mov(r3, Operand(r0), SetCC);
   __ b(eq, loop_statement.continue_target());
 
   // Update the 'each' property or variable from the possibly filtered
   // entry in register r3.
   __ bind(&update_each);
   __ mov(result_register(), r3);
   // Perform the assignment as if via '='.
   EmitAssignment(stmt->each());
 
   // Generate code for the body of the loop.
@@ skipping 2243 matching lines @@
   __ mov(r1, Operand(r1, ASR, 1));  // Un-smi-tag value.
   __ add(pc, r1, Operand(masm_->CodeObject()));
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM