Remove expired histogram Discarding.OnlineOnReload.*

Fixed: 1088709
Change-Id: If79d2cfe4fa188e2b3bfd86b9ed6c7a7f0b8e69c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2526906
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825847}

chrome/browser/resource_coordinator/discard_metrics_lifecycle_unit_observer.cc

@@ -12,20 +12,9 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/resource_coordinator/lifecycle_unit.h"
 #include "chrome/browser/resource_coordinator/time.h"
-#include "net/base/network_change_notifier.h"
 
 namespace resource_coordinator {
 
-namespace {
-
-void RecordReloadAfterDiscardHistograms(const char* reason) {
-  base::UmaHistogramBoolean(
-      base::JoinString({"Discarding.OnlineOnReload", reason}, "."),
-      !net::NetworkChangeNotifier::IsOffline());
-}
-
-}  // namespace
-
 DiscardMetricsLifecycleUnitObserver::DiscardMetricsLifecycleUnitObserver() =
     default;
 DiscardMetricsLifecycleUnitObserver::~DiscardMetricsLifecycleUnitObserver() =
@@ -88,20 +77,6 @@ void DiscardMetricsLifecycleUnitObserver::OnReload() {
   UMA_HISTOGRAM_CUSTOM_TIMES(
       "TabManager.Discarding.InactiveToReloadTime", inactive_to_reload_time,
       base::TimeDelta::FromSeconds(1), base::TimeDelta::FromDays(1), 100);
-
-  // TODO(fdoray): All discard histograms should have a reason suffix.
-  switch (discard_reason_) {
-    case LifecycleUnitStateChangeReason::SYSTEM_MEMORY_PRESSURE:
-      RecordReloadAfterDiscardHistograms("Urgent");
-      break;
-    case LifecycleUnitStateChangeReason::EXTENSION_INITIATED:
-      RecordReloadAfterDiscardHistograms("Extension");
-      break;
-    case LifecycleUnitStateChangeReason::BROWSER_INITIATED:
-    default:
-      NOTREACHED();
-      break;
-  }
 }
 
 }  // namespace resource_coordinator

tools/metrics/histograms/histograms_xml/histogram_suffixes_list.xml

@@ -5087,6 +5087,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram_suffixes>
 
 <histogram_suffixes name="DiscardReason" separator=".">
+  <obsolete>
+    Removed 11/2020. All affected histograms were removed.
+  </obsolete>
   <suffix name="Extension" label="An extension discarded a tab."/>
   <suffix name="Proactive"
       label="The browser proactively discarded a tab to avoid entering a

tools/metrics/histograms/histograms_xml/others/histograms.xml

@@ -3802,6 +3802,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="Discarding.OnlineOnReload" enum="Boolean" expires_after="M85">
+  <obsolete>
+    Removed 11/2020.
+  </obsolete>
 <!-- Name completed by histogram_suffixes name="DiscardReason" -->
 
   <owner>fdoray@chromium.org</owner>