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

test/mjsunit/regress/regress-crbug-387599.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 --expose-debug-as debug
 
 Debug = debug.Debug;
 Debug.setListener(function() {});
 
 function f() {
-  for (var i = 0; i < 100; i++) {
-    %OptimizeFunctionOnNextCall(f, "osr");
-  }
+  for (var i = 0; i < 100; i++) %OptimizeOsr();
 }
 
 Debug.setBreakPoint(f, 0, 0);
 f();
 f();
 Debug.setListener(null);