Make closures optimizable by Crankshaft compiler.

test/mjsunit/regress/regress-create-exception.js

 // Copyright 2010 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 31 matching lines @@
       // garbage collector.  93 is chosen to be a prime number to avoid the
       // allocation settling into a too neat pattern.
       for (var j = 0; j < i % 93; j++) {
         j *= 1.123567;  // An arbitrary floating point number.
       }
       v[0x7fffffff] = 0;  // Trigger exception.
       assertTrue(false);
       return j;  // Make sure that future optimizations don't eliminate j.
     } catch(e) {
       ok = true;
-      assertTrue(re.test(e));
+      assertTrue(re.test(e), 'e: ' + e);
     }
     assertTrue(ok);
   }
 }
 
 foo();