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

test/mjsunit/array-shift4.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
 
 // Inlining shift with holey smi arrays shouldn't deopt just because it
 // encounters the hole on the copy step.
 function doShift(a) {
   var x = a.shift();
   return x;
 }
 
 function makeArray() {
   var a = [1, 2,, 3];
   a[0] = 2;
   return a;
 }
 
 doShift(makeArray());
 doShift(makeArray());
 %OptimizeFunctionOnNextCall(doShift);
 doShift(makeArray());
 assertOptimized(doShift);