Add delay to canary check at browser start for IsolatedPrerender

Previous CL didn't improve browser startup latency, trying this.

Bug: 1113691
Change-Id: I0264cf566faf3b8a1ec118217ec16582cee5a020
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354918
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Auto-Submit: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797909}

chrome/browser/prerender/isolated/isolated_prerender_origin_prober.cc

@@ -165,8 +165,10 @@ IsolatedPrerenderOriginProber::IsolatedPrerenderOriginProber(Profile* profile)
   // the chance, but there's no point in it being ready for the first navigation
   // since the check won't be done by then anyways.
   content::GetUIThreadTaskRunner({base::TaskPriority::BEST_EFFORT})
-      ->PostTask(FROM_HERE,
-                 base::BindOnce(&StartCanaryCheck, canary_check_->AsWeakPtr()));
+      ->PostDelayedTask(
+          FROM_HERE,
+          base::BindOnce(&StartCanaryCheck, canary_check_->AsWeakPtr()),
+          base::TimeDelta::FromSeconds(1));
 }
 
 IsolatedPrerenderOriginProber::~IsolatedPrerenderOriginProber() = default;