Merge r10190 to 3.7 branch: Fix a bug with register use in optimized Math.round.

test/mjsunit/compiler/regress-106351.js

 // Copyright 2011 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 18 matching lines @@
 
 // Test Math.round with the input reused in the same expression.
 function test(x) {
   var v = Math.round(x) - x;
   assertEquals(0.5, v);
 }
 
 for (var i = 0; i < 5; ++i) test(0.5);
 %OptimizeFunctionOnNextCall(test);
 test(0.5);