[test] Speed up some slow tests.

test/mjsunit/math-floor-part2.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 91 matching lines @@
   testFloor(-two_30, -two_30 + 0.7);
 
   testFloor(-two_30 + 1, -two_30 + 1);
   testFloor(-two_30 + 1, -two_30 + 1 + 0.1);
   testFloor(-two_30 + 1, -two_30 + 1 + 0.5);
   testFloor(-two_30 + 1, -two_30 + 1 + 0.7);
 }
 
 
 // Test in a loop to cover the custom IC and GC-related issues.
-for (var i = 0; i < 100; i++) {
+for (var i = 0; i < 10; i++) {
   test();
+  new Array(i * 10000);
 }