Increase cushion in timeOrigin test

This CL makes comparisons with Date() in timeOrigin.html easier to pass.
See the following relevant discussions:

https: //github.com/w3c/web-platform-tests/pull/6822#discussion_r135601415
https: //github.com/w3c/web-platform-tests/issues/7075
Change-Id: Ic676eeea04b9717a3460acfbeebf8d2ed3207d4f
Reviewed-on: https://chromium-review.googlesource.com/646070
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Nicolás Peña <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498966}
diff --git a/hr-time/timeOrigin.html b/hr-time/timeOrigin.html
index 415d745..20aea75 100644
--- a/hr-time/timeOrigin.html
+++ b/hr-time/timeOrigin.html
@@ -9,10 +9,11 @@
 const windowOrigin = performance.timeOrigin;
 
 test(() => {
+  // Use a 30ms cushion when comparing with Date() to account for inaccuracy.
   const startTime = Date.now();
-  assert_greater_than_equal(startTime + 1, windowOrigin, 'Date.now() should be at least as large as the window timeOrigin.');
+  assert_greater_than_equal(startTime + 30, windowOrigin, 'Date.now() should be at least as large as the window timeOrigin.');
   const startNow = performance.now();
-  assert_less_than_equal(startTime, windowOrigin + startNow + 1, 'Date.now() should be close to window timeOrigin.');
+  assert_less_than_equal(startTime, windowOrigin + startNow + 30, 'Date.now() should be close to window timeOrigin.');
 }, 'Window timeOrigin is close to Date.now() when there is no system clock adjustment.');
 
 const workerScript = 'postMessage({timeOrigin: performance.timeOrigin})';