Added %NeverOptimize runtime call that can disable optimizations for a method for tests.

test/mjsunit/regress/regress-deopt-gcb.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 22 matching lines @@
 
 // Ensure that there is code objects before the code for the opt_me function.
 (function() { var a = 10; a++; })();
 
 function opt_me() {
   deopt();
 }
 
 function deopt() {
   // Make sure we don't inline this function
-  try { var a = 42; } catch(o) {};
+  %NeverOptimize();
   %DeoptimizeFunction(opt_me);
   gc();
 }
 
 
 opt_me();