Fix ARM bug introduced in r12604 that caused crashes on ARM

src/arm/macro-assembler-arm.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 798 matching lines @@
                             Register scratch,
                             Label* fail);
 
   // Check to see if maybe_number can be stored as a double in
   // FastDoubleElements. If it can, store it at the index specified by key in
   // the FastDoubleElements array elements. Otherwise jump to fail, in which
   // case scratch2, scratch3 and scratch4 are unmodified.
   void StoreNumberToDoubleElements(Register value_reg,
                                    Register key_reg,
                                    Register receiver_reg,
+                                   // All regs below here overwritten.
                                    Register elements_reg,
                                    Register scratch1,
                                    Register scratch2,
                                    Register scratch3,
                                    Register scratch4,
                                    Label* fail);
 
   // Compare an object's map with the specified map and its transitioned
   // elements maps if mode is ALLOW_ELEMENT_TRANSITION_MAPS. Condition flags are
   // set with result of map compare. If multiple map compares are required, the
@@ skipping 571 matching lines @@
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ARM_MACRO_ASSEMBLER_ARM_H_