Add infrastructure for skipping tests in GC stress mode.

test/mjsunit/d8-performance-now.js

Index: test/mjsunit/d8-performance-now.js
diff --git a/test/mjsunit/d8-performance-now.js b/test/mjsunit/d8-performance-now.js
index 13eb1d3f006fa9405873d7e191d733bc4ac37b02..3e5485e81d943c4e0f49a431465284e7aff1b1e2 100644
--- a/test/mjsunit/d8-performance-now.js
+++ b/test/mjsunit/d8-performance-now.js
@@ -30,11 +30,6 @@
 // Test the performance.now() function of d8.  This test only makes sense with
 // d8.
 
-// Don't run this test in gc stress mode. Time differences may be long
-// due to garbage collections.
-%SetFlags("--gc-interval=-1");
-%SetFlags("--nostress-compaction");
-
 if (this.performance && performance.now) {
   (function run() {
     var start_test = performance.now();