Revert "Add Metrics about Uploading UMA Records from Previous Sessions"

This reverts commit aa74ca79.

Reason for revert:

Due to a bug in the original changelist, these histograms were never emitted.  In particular, they weren't emitted because the implementation classes (the ones that actually emit the metrics) aren't part of the class.  In other words, they're not overriding the parent class behavior and thus not getting called.

When I fixed the bug and tested the fix, I realized that the way I hooked up the metrics emitting code is wrong.  I expected the UnsentLogs.Sent-emitting code to be run only when persisted logs (logs from past sessions) were going to be sent.  However, it records all logs that are sent, not only persisted ones.  For example, it records (i) the initial stability log and (ii) the logs that happen at regular intervals.  Neither of those are counted in UnsentLogs.IntendingToSend.

Long story short: bug in original changelist.  Fixing the bug is non-trivial and requires substantial changes.  Reverting to start over fro a clean slate.

Reverting the histograms.xml change is safe because these histograms were never logged.

BUG=1148523

Original change's description:
> Add Metrics about Uploading UMA Records from Previous Sessions
>
> Change-Id: I908a337129062e882b185a08329fecfd7db6c496
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2504593
> Reviewed-by: Steven Holte <holte@chromium.org>
> Commit-Queue: Mark Pearson <mpearson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#822037}

TBR=mpearson@chromium.org,holte@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Ie44b8bac5948cb19af245800ac42e6b5bab11996
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537604Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827872}

components/metrics/unsent_log_store.cc

@@ -162,7 +162,6 @@ void UnsentLogStore::MarkStagedLogAsSent() {
   DCHECK_LT(static_cast<size_t>(staged_log_index_), list_.size());
   if (list_[staged_log_index_]->samples_count.has_value())
     total_samples_sent_ += list_[staged_log_index_]->samples_count.value();
-  metrics_->RecordSentLog();
 }
 
 void UnsentLogStore::TrimAndPersistUnsentLogs() {
@@ -304,7 +303,6 @@ void UnsentLogStore::TrimLogs() {
   size_t dropped_logs_count = list_.size() - trimmed_list.size();
   if (dropped_logs_count > 0)
     metrics_->RecordDroppedLogsNum(dropped_logs_count);
-  metrics_->RecordIntendingToSentLogs(trimmed_list.size());
 
   // Put the trimmed list in the correct place.
   list_.swap(trimmed_list);

components/metrics/unsent_log_store_metrics.cc

@@ -22,10 +22,6 @@ void UnsentLogStoreMetrics::RecordDroppedLogSize(size_t size) {}
 
 void UnsentLogStoreMetrics::RecordDroppedLogsNum(int dropped_logs_num) {}
 
-void UnsentLogStoreMetrics::RecordIntendingToSentLogs(int num) {}
-
-void UnsentLogStoreMetrics::RecordSentLog() {}
-
 void UnsentLogStoreMetrics::RecordLastUnsentLogMetadataMetrics(
     int unsent_samples_count,
     int sent_samples_count,

components/metrics/unsent_log_store_metrics.h

@@ -40,21 +40,10 @@ class UnsentLogStoreMetrics {
   virtual void RecordCompressionRatio(size_t compressed_size,
                                       size_t original_size);
 
-  // Records the size of a dropped log in bytes.
   virtual void RecordDroppedLogSize(size_t size);
 
-  // Record the number of logs that were dropped (not staged).  These include
-  // logs that were dropped due to be being too large and also logs that were
-  // dropped because there were too many.
   virtual void RecordDroppedLogsNum(int dropped_logs_num);
 
-  // Records the number of logs that were not dropped and instead staged /
-  // intended to be sent.
-  virtual void RecordIntendingToSentLogs(int num);
-
-  // Record when a single staged log was sent.
-  virtual void RecordSentLog();
-
   virtual void RecordLastUnsentLogMetadataMetrics(int unsent_samples_count,
                                                   int sent_samples_count,
                                                   int persisted_size_in_kb);

components/metrics/unsent_log_store_metrics_impl.cc

@@ -31,14 +31,6 @@ void UnsentLogStoreMetricsImpl::RecordDroppedLogsNum(int dropped_logs_num) {
   base::UmaHistogramCounts1M("UMA.UnsentLogs.Dropped", dropped_logs_num);
 }
 
-void RecordIntendingToSentLogs(int num) {
-  base::UmaHistogramExactLinear("UMA.UnsentLogs.IntendingToSend", num, 22);
-}
-
-void RecordSentLog() {
-  base::UmaHistogramBoolean("UMA.UnsentLogs.Sent", true);
-}
-
 void UnsentLogStoreMetricsImpl::RecordLastUnsentLogMetadataMetrics(
     int unsent_samples_count,
     int sent_samples_count,

tools/metrics/histograms/histograms_xml/uma/histograms.xml

@@ -584,13 +584,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
     expires_after="2021-08-30">
   <owner>holte@chromium.org</owner>
   <owner>asvitkine@chromium.org</owner>
-  <owner>mpearson@chromium.org</owner>
   <owner>src/base/metrics/OWNERS</owner>
   <summary>
-    The number of UMA unsent logs removed from persistent storage.
-
-    Useful in comparison with UMA.UnsentLogs.IntendingToSend (that counts hte
-    number of UMA unsent logs that are intended to be sent, i.e., not dropped).
+    Counter for number of UMA unsent logs removed from persistent storage.
   </summary>
 </histogram>
 
@@ -608,20 +604,6 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
-<histogram name="UMA.UnsentLogs.IntendingToSend" units="logs"
-    expires_after="2021-04-01">
-  <owner>mpearson@chromium.org</owner>
-  <owner>src/base/metrics/OWNERS</owner>
-  <summary>
-    The number of UMA unsent logs from persistent storage that will be staged /
-    are intended to be sent. These logs are not dropped from persistent storage.
-
-    Useful in comparison with UMA.UnsentLogs.Dropped (to see how many persistent
-    logs are intended to be sent versus are not intended to be sent) and with
-    UMA.UnsentLogs.IntendingToSend (to see how many are actually sent).
-  </summary>
-</histogram>
-
 <histogram name="UMA.UnsentLogs.PersistedSizeInKB" units="KB"
     expires_after="2021-05-30">
   <owner>michaelbai@chromium.org</owner>
@@ -634,17 +616,6 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
-<histogram name="UMA.UnsentLogs.Sent" enum="Boolean" expires_after="2021-04-01">
-  <owner>mpearson@chromium.org</owner>
-  <owner>src/base/metrics/OWNERS</owner>
-  <summary>
-    Emitted when a UMA unsent log is marked as sent.
-
-    Useful in comparison with UMA.UnsentLogs.Dropped and
-    UMA.UnsentLogs.IntendingToSend.
-  </summary>
-</histogram>
-
 <histogram name="UMA.UnsentLogs.SentCount" units="samples"
     expires_after="2021-05-30">
   <owner>michaelbai@chromium.org</owner>