Remove obsolete Event.Latency.Scroll.Wheel.TimeToScrollUpdateSwapBegin2

This histogram tracks the time from all wheel events to when the
swap begins for the resulting frame. However, we typically only look at
the more specific
Event.Latency.Scroll(Begin|Update).Wheel.TimeToScrollUpdateSwapBegin4
metrics which reflect the same values.

Bug: 1081296
Change-Id: Ibd1fd7dd684c31405d4cbdad98216ca82553d760
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627765
Commit-Queue: Robert Flack <flackr@chromium.org>
Reviewed-by: Mustaq Ahmed <mustaq@chromium.org>
Reviewed-by: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#845264}

content/browser/renderer_host/input/render_widget_host_latency_tracker_unittest.cc

@@ -197,8 +197,6 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, TestValidEventTiming) {
   // of the start_component, zero is recorded instead of a negative value.
   histogram_tester().ExpectUniqueSample(
       "Event.Latency.ScrollBegin.Wheel.TimeToScrollUpdateSwapBegin4", 0, 1);
-  histogram_tester().ExpectUniqueSample(
-      "Event.Latency.Scroll.Wheel.TimeToScrollUpdateSwapBegin2", 0, 1);
   histogram_tester().ExpectUniqueSample(
       "Event.Latency.ScrollBegin.Wheel.TimeToHandled2_Impl", 0, 1);
   histogram_tester().ExpectUniqueSample(
@@ -272,10 +270,6 @@ TEST_F(RenderWidgetHostLatencyTrackerTest,
           HistogramSizeEq("Event.Latency.ScrollBegin.Wheel."
                           "TimeToScrollUpdateSwapBegin4",
                           1));
-      EXPECT_TRUE(
-          HistogramSizeEq("Event.Latency.Scroll.Wheel."
-                          "TimeToScrollUpdateSwapBegin2",
-                          1));
       EXPECT_TRUE(
           HistogramSizeEq("Event.Latency.ScrollUpdate.Wheel."
                           "TimeToScrollUpdateSwapBegin4",
@@ -386,10 +380,6 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, MAYBE_TestWheelToScrollHistograms) {
           HistogramSizeEq("Event.Latency.ScrollBegin.Wheel."
                           "TimeToScrollUpdateSwapBegin4",
                           0));
-      EXPECT_TRUE(
-          HistogramSizeEq("Event.Latency.Scroll.Wheel."
-                          "TimeToScrollUpdateSwapBegin2",
-                          1));
       EXPECT_TRUE(
           HistogramSizeEq("Event.Latency.ScrollUpdate.Wheel."
                           "TimeToScrollUpdateSwapBegin4",

tools/metrics/histograms/histograms_xml/event/histograms.xml

@@ -432,6 +432,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 
 <histogram name="Event.Latency.Scroll.Wheel.TimeToScrollUpdateSwapBegin2"
     units="microseconds" expires_after="2020-06-21">
+  <obsolete>
+    Removed 2021-01-14 - replaced by Event.Latency.Scroll(Begin|Update).Wheel.*.
+  </obsolete>
   <owner>flackr@chromium.org</owner>
   <summary>
     Time between initial creation of a wheel event and start of the frame swap

ui/latency/latency_info.dot

@@ -17,7 +17,6 @@ Event.Latency.EndToEnd.TouchpadPinch\n"];
       [label="\
 Event.Latency.<scroll_name>.TimeToScrollUpdateSwapBegin2\n\
 Event.Latency.<scroll_name>.<input_modality>.TimeToScrollUpdateSwapBegin4\n\
-Event.Latency.Scroll.Wheel.TimeToScrollUpdateSwapBegin2\n\
 UKM: Event.<scroll_name>.<input_modality>.TimeToScrollUpdateSwapBegin\n"]
     scroll_to_schedule_metrics
       [label="\

ui/latency/latency_tracker.cc

@@ -50,19 +50,6 @@ bool IsInertialScroll(const LatencyInfo& latency) {
   return latency.source_event_type() == ui::SourceEventType::INERTIAL;
 }
 
-// This UMA metric tracks the time from when the original wheel event is created
-// to when the scroll gesture results in final frame swap. All scroll events are
-// included in this metric.
-void RecordUmaEventLatencyScrollWheelTimeToScrollUpdateSwapBegin2Histogram(
-    base::TimeTicks start,
-    base::TimeTicks end) {
-  CONFIRM_EVENT_TIMES_EXIST(start, end);
-  UMA_HISTOGRAM_CUSTOM_COUNTS(
-      "Event.Latency.Scroll.Wheel.TimeToScrollUpdateSwapBegin2",
-      std::max(static_cast<int64_t>(0), (end - start).InMicroseconds()), 1,
-      1000000, 100);
-}
-
 bool LatencyTraceIdCompare(const LatencyInfo& i, const LatencyInfo& j) {
   return i.trace_id() < j.trace_id();
 }
@@ -211,11 +198,6 @@ void LatencyTracker::ComputeEndToEndLatencyHistograms(
     UMA_HISTOGRAM_INPUT_LATENCY_5_SECONDS_MAX_MICROSECONDS(
         metric_name, original_timestamp, gpu_swap_begin_timestamp);
 
-    if (input_modality == "Wheel") {
-      RecordUmaEventLatencyScrollWheelTimeToScrollUpdateSwapBegin2Histogram(
-          original_timestamp, gpu_swap_begin_timestamp);
-    }
-
   } else if (latency.FindLatency(
                  ui::INPUT_EVENT_LATENCY_SCROLL_UPDATE_ORIGINAL_COMPONENT,
                  &original_timestamp)) {
@@ -254,10 +236,6 @@ void LatencyTracker::ComputeEndToEndLatencyHistograms(
     UMA_HISTOGRAM_INPUT_LATENCY_5_SECONDS_MAX_MICROSECONDS(
         metric_name, original_timestamp, gpu_swap_begin_timestamp);
 
-    if (input_modality == "Wheel") {
-      RecordUmaEventLatencyScrollWheelTimeToScrollUpdateSwapBegin2Histogram(
-          original_timestamp, gpu_swap_begin_timestamp);
-    }
   } else if (latency.FindLatency(ui::INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT,
                                  &original_timestamp)) {
     if (latency.source_event_type() == SourceEventType::KEY_PRESS) {