Quota: remove unused histograms

This CL removes the following histograms. They are
expiring, and have not been looked at in a while.
They also don't seem to provide too much valuable
information on eviction, therefore removing.

- Quota.TimeDeltaOfEvictionRounds
- Quota.SkippedEvictionRoundsPerHour

OBSOLETE_HISTOGRAMS=Histograms expiring and unused

Bug: 346341974
Change-Id: If145811ca82cbc0164ed5eae5caf08cdd625ef77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5723111
Reviewed-by: Evan Stade <estade@chromium.org>
Commit-Queue: Ayu Ishii <ayui@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1333592}

storage/browser/quota/quota_temporary_storage_evictor.cc

@@ -66,13 +66,6 @@ void QuotaTemporaryStorageEvictor::ReportPerRoundHistogram() {
   base::Time now = base::Time::Now();
   base::UmaHistogramTimes("Quota.TimeSpentToAEvictionRound",
                           now - round_statistics_.start_time);
-  if (!time_of_end_of_last_round_.is_null()) {
-    base::UmaHistogramCustomTimes("Quota.TimeDeltaOfEvictionRounds",
-                                  now - time_of_end_of_last_round_,
-                                  base::Minutes(1), base::Days(1), 50);
-  }
-  time_of_end_of_last_round_ = now;
-
   UmaHistogramMbytes("Quota.DiskspaceShortage",
                      round_statistics_.diskspace_shortage_at_round);
   UmaHistogramMbytes("Quota.EvictedBytesPerRound",
@@ -92,8 +85,6 @@ void QuotaTemporaryStorageEvictor::ReportPerHourHistogram() {
                              stats_in_hour.num_evicted_buckets);
   base::UmaHistogramCounts1M("Quota.EvictionRoundsPerHour",
                              stats_in_hour.num_eviction_rounds);
-  base::UmaHistogramCounts1M("Quota.SkippedEvictionRoundsPerHour",
-                             stats_in_hour.num_skipped_eviction_rounds);
 }
 
 void QuotaTemporaryStorageEvictor::OnEvictionRoundStarted() {

storage/browser/quota/quota_temporary_storage_evictor.h

@@ -98,7 +98,6 @@ class COMPONENT_EXPORT(STORAGE_BROWSER) QuotaTemporaryStorageEvictor {
   Statistics previous_statistics_;
   EvictionRoundStatistics round_statistics_;
   base::Time time_of_end_of_last_nonskipped_round_;
-  base::Time time_of_end_of_last_round_;
 
   int64_t interval_ms_;
   bool timer_disabled_for_testing_ = false;

tools/metrics/histograms/metadata/quota/histograms.xml

@@ -318,16 +318,6 @@ chromium-metrics-reviews@google.com.
   </summary>
 </histogram>
 
-<histogram name="Quota.SkippedEvictionRoundsPerHour" units="units"
-    expires_after="2024-07-21">
-  <owner>ayui@chromium.org</owner>
-  <owner>chrome-owp-storage@google.com</owner>
-  <summary>
-    Number of skipped eviction rounds in an hour. Histogram expired between
-    2018/08 and 2022/06.
-  </summary>
-</histogram>
-
 <histogram name="Quota.SkippedInvalidOriginUsage" enum="InvalidOriginReason"
     expires_after="2024-08-24">
   <owner>ayui@chromium.org</owner>
@@ -366,16 +356,6 @@ chromium-metrics-reviews@google.com.
   </summary>
 </histogram>
 
-<histogram name="Quota.TimeDeltaOfEvictionRounds" units="units"
-    expires_after="2024-07-21">
-  <owner>ayui@chromium.org</owner>
-  <owner>chrome-owp-storage@google.com</owner>
-  <summary>
-    Time between two consecutive eviction rounds. Only recorded if at least one
-    origin has been evicted in each eviction round.
-  </summary>
-</histogram>
-
 <histogram name="Quota.TimeSpentToAEvictionRound" units="units"
     expires_after="2025-05-19">
   <owner>ayui@chromium.org</owner>