Handle negative input in inlined Math.round on Intel CPUs.

test/mjsunit/regress/regress-2451.js

Index: test/mjsunit/regress/regress-2451.js
diff --git a/test/mjsunit/regress/regress-crbug-173974.js b/test/mjsunit/regress/regress-2451.js
similarity index 90%
copy from test/mjsunit/regress/regress-crbug-173974.js
copy to test/mjsunit/regress/regress-2451.js
index 905bd6058a0ad0fe2ebe10e4c7dafbe9945cbe3b..465e4e68c26f3e3e119cbaf82d50c8f83c6efa9a 100644
--- a/test/mjsunit/regress/regress-crbug-173974.js
+++ b/test/mjsunit/regress/regress-2451.js
@@ -28,9 +28,14 @@
 // Flags: --allow-natives-syntax
 
 function f() {
-  var count = "";
-  count[0] --;
+  assertEquals(-1.0, Math.round(-1.5));
+  assertEquals(-2.0, Math.round(-2.5));
+  assertEquals(-1.0, Math.round(-0.5000000000000001));
 }
+
+f();
 f();
 %OptimizeFunctionOnNextCall(f);
 f();
+assertTrue(%GetOptimizationStatus(f) != 2);
+