[mjsunit] Improve long-running test

Reading up on the bug description, this is a test
that is triggered by TurboFan execution. This can
be done with natives and does not need excessive
loop iterations. Additionally, we have a more specific
regression test for the original issue in the repo:
http://crrev.com/c/584837

Bug: v8:7783
Change-Id: Id022b515b663e6fb897acb29f43ef92b70b547b8
Reviewed-on: https://chromium-review.googlesource.com/1101018Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53799}

test/mjsunit/regress/regress-747075.js

@@ -2,13 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --allow-natives-syntax
+
 r = [
   14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
   14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14
 ];
 
 
-for (i = -1; i < 100000; i++) {
+function f() {
   r2 = r.map(function(y) {return y/64} );
   assertTrue(r2[0] < 1);
 }
+
+for (let i = 0; i < 1000; ++i) f();
+for (let i = 0; i < 1000; ++i) f();
+%OptimizeFunctionOnNextCall(f);
+for (let i = 0; i < 1000; ++i) f();