Do not eagerly update allow_osr_at_loop_nesting_level.

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");
+  }
+}
+
+Debug.setBreakPoint(f, 0, 0);
+f();
+f();
+Debug.setListener(null);