Make it easier to test OSR with %OptimizeOsr() runtime call.

test/mjsunit/regress/regress-379770.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 --nostress-opt
 // Flags: --nouse-osr
 
 function foo(obj) {
   var counter = 1;
-  for (var i = 0; i < obj.length; i++) {
-    %OptimizeFunctionOnNextCall(foo, "osr");
-  }
+  for (var i = 0; i < obj.length; i++) %OptimizeOsr();
   counter += obj;
   return counter;
 }
 
 function bar() {
   var a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12];
   for (var i = 0; i < 100; i++ ) {
     foo(a);
   }
 }
 
 try {
   bar();
 } catch (e) {
 }