[about:flags] Intensive JS Timer Throttling: Enable after 10 seconds instead of immediately.

Normally, Intensive JS Timer Throttling is enabled when a tab has been
hidden for 5 minutes. To facilitate testing, about:flags provides an
option to enable the intervention immediately when a tab is hidden.
Unfortunately, this affects timers set with a short timeout from the
visibilitychange event and leads to unrealistic test condition. To
provide more realistic test conditions, this CL changes the
about:flags entry to enable the intervention when a tab has been
hidden for 10 seconds.

Bug: 1075553
Change-Id: I4594e920c3214d7e335851b941acb9bbe85aac65
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2399305Reviewed-by: Alexander Timin <altimin@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805296}

chrome/browser/about_flags.cc

@@ -569,13 +569,14 @@ const FeatureEntry::FeatureVariation
          kDelayCompetingLowPriorityRequestsRelaxedAlways,
          base::size(kDelayCompetingLowPriorityRequestsRelaxedAlways), nullptr}};
 
-const FeatureEntry::FeatureParam kIntensiveWakeUpThrottlingImmediate[] = {
-    {blink::features::kIntensiveWakeUpThrottling_GracePeriodSeconds_Name, "0"}};
+const FeatureEntry::FeatureParam kIntensiveWakeUpThrottlingAfter10Seconds[] = {
+    {blink::features::kIntensiveWakeUpThrottling_GracePeriodSeconds_Name,
+     "10"}};
 
 const FeatureEntry::FeatureVariation kIntensiveWakeUpThrottlingVariations[] = {
-    {"immediately when a tab is hidden (facilitates testing)",
-     kIntensiveWakeUpThrottlingImmediate,
-     base::size(kIntensiveWakeUpThrottlingImmediate), nullptr},
+    {"10 seconds after a tab is hidden (facilitates testing)",
+     kIntensiveWakeUpThrottlingAfter10Seconds,
+     base::size(kIntensiveWakeUpThrottlingAfter10Seconds), nullptr},
 };
 
 #if defined(OS_ANDROID)