Remove the kBrowserHangFixesExperiment experiment

Now that there's longer any experiments with shutdown hangs, this CL
removes the feature flag and defaults the background task runners of
the incident reporting service to CONTINUE_ON_SHUTDOWN

Bug: 478209
Change-Id: Iec41d087911fadf518d4537da942ed7939b1aa11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1954196Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Patrick Monette <pmonette@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722521}

chrome/browser/safe_browsing/incident_reporting/incident_reporting_service.cc

@@ -36,7 +36,6 @@
 #include "chrome/browser/safe_browsing/incident_reporting/preference_validation_delegate.h"
 #include "chrome/browser/safe_browsing/incident_reporting/state_store.h"
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
-#include "chrome/common/chrome_features.h"
 #include "chrome/common/pref_names.h"
 #include "components/prefs/pref_service.h"
 #include "components/safe_browsing/common/safe_browsing_prefs.h"
@@ -124,20 +123,11 @@ PersistentIncidentState ComputeIncidentState(const Incident& incident) {
   return state;
 }
 
-// Returns the shutdown behavior for the task runners of the incident reporting
-// service. Current metrics suggest that CONTINUE_ON_SHUTDOWN will reduce the
-// number of browser hangs on shutdown.
-base::TaskShutdownBehavior GetShutdownBehavior() {
-  return base::FeatureList::IsEnabled(features::kBrowserHangFixesExperiment)
-             ? base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN
-             : base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN;
-}
-
 // Returns a task runner for blocking tasks in the background.
 scoped_refptr<base::TaskRunner> GetBackgroundTaskRunner() {
-  return base::CreateTaskRunner({base::ThreadPool(),
-                                 base::TaskPriority::BEST_EFFORT,
-                                 GetShutdownBehavior(), base::MayBlock()});
+  return base::CreateTaskRunner(
+      {base::ThreadPool(), base::TaskPriority::BEST_EFFORT,
+       base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN, base::MayBlock()});
 }
 
 }  // namespace

chrome/common/chrome_features.cc

@@ -106,11 +106,6 @@ const base::Feature kBlockRepeatedNotificationPermissionPrompts{
     "BlockRepeatedNotificationPermissionPrompts",
     base::FEATURE_ENABLED_BY_DEFAULT};
 
-// Fixes for browser hang bugs are deployed in a field trial in order to measure
-// their impact. See crbug.com/478209.
-const base::Feature kBrowserHangFixesExperiment{
-    "BrowserHangFixesExperiment", base::FEATURE_DISABLED_BY_DEFAULT};
-
 // Enables or disables redirecting users who get an interstitial when
 // accessing https://support.google.com/chrome/answer/6098869 to local
 // connection help content.

chrome/common/chrome_features.h

@@ -75,9 +75,6 @@ extern const base::Feature kBlockPromptsIfIgnoredOften;
 COMPONENT_EXPORT(CHROME_FEATURES)
 extern const base::Feature kBlockRepeatedNotificationPermissionPrompts;
 
-COMPONENT_EXPORT(CHROME_FEATURES)
-extern const base::Feature kBrowserHangFixesExperiment;
-
 COMPONENT_EXPORT(CHROME_FEATURES)
 extern const base::Feature kBundledConnectionHelpFeature;