[tests] Cleanup tests that use assertOptimized()/assertUnoptimized().

test/mjsunit/regress/regress-3176.js

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --crankshaft
 
 function foo(a) {
   var sum = 0;
   for (var i = 0; i < 10; i++) {
     sum += a[i];
 
     if (i > 6) {
       sum -= a[i - 4];
       sum -= a[i - 5];
     }
   }
   return sum;
 }
 
 var a = new Int32Array(10);
 
 foo(a);
 foo(a);
 %OptimizeFunctionOnNextCall(foo);
 foo(a);
 %OptimizeFunctionOnNextCall(foo);
 foo(a);
 assertOptimized(foo);