Add ScrollBegin.Touch/Wheel Event to UKM

Report ScrollBegin.wheel/touch TimeToScrollUpdateSwapBegin
via UKM. And add test for them.

BUG=719605, 728707

Review-Url: https://codereview.chromium.org/2924943004
Cr-Commit-Position: refs/heads/master@{#479496}

content/browser/renderer_host/input/render_widget_host_latency_tracker_unittest.cc

@@ -146,6 +146,7 @@ class RenderWidgetHostLatencyTrackerTest
                                                const char* metric_name) {
     const ukm::TestUkmRecorder* ukm_recoder =
         test_browser_client_.GetTestUkmRecorder();
+
     size_t actual_event_count = 0;
     for (size_t i = 0; i < ukm_recoder->entries_count(); ++i) {
       const ukm::mojom::UkmEntry* entry = ukm_recoder->GetEntry(i);
@@ -226,6 +227,7 @@ class RenderWidgetHostLatencyTrackerTest
 
 TEST_F(RenderWidgetHostLatencyTrackerTest, TestWheelToFirstScrollHistograms) {
   const GURL url(kUrl);
+  size_t total_ukm_entry_count = 0;
   contents()->NavigateAndCommit(url);
   for (bool rendering_on_main : {false, true}) {
     ResetHistograms();
@@ -250,6 +252,10 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, TestWheelToFirstScrollHistograms) {
                                  INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
       tracker()->OnGpuSwapBuffersCompleted(wheel_latency);
 
+      // UKM metrics.
+      total_ukm_entry_count++;
+      EXPECT_TRUE(AssertUkmReported("Event.ScrollBegin.Wheel",
+                                    "TimeToScrollUpdateSwapBegin"));
       // Rappor metrics.
       EXPECT_TRUE(
           RapporSampleAssert("Event.Latency.ScrollUpdate.Touch."
@@ -316,8 +322,8 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, TestWheelToFirstScrollHistograms) {
 
       ukm::TestUkmRecorder* test_ukm_recorder =
           test_browser_client_.GetTestUkmRecorder();
-      EXPECT_EQ(0U, test_ukm_recorder->sources_count());
-      EXPECT_EQ(0U, test_ukm_recorder->entries_count());
+      EXPECT_EQ(1U, test_ukm_recorder->sources_count());
+      EXPECT_EQ(total_ukm_entry_count, test_ukm_recorder->entries_count());
     }
   }
 }
@@ -398,6 +404,7 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, TestWheelToScrollHistograms) {
 TEST_F(RenderWidgetHostLatencyTrackerTest, TestTouchToFirstScrollHistograms) {
   const GURL url(kUrl);
   contents()->NavigateAndCommit(url);
+  size_t total_ukm_entry_count = 0;
   for (bool rendering_on_main : {false, true}) {
     ResetHistograms();
     {
@@ -443,6 +450,10 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, TestTouchToFirstScrollHistograms) {
       tracker()->OnGpuSwapBuffersCompleted(touch_latency);
     }
 
+    // UKM metrics.
+    total_ukm_entry_count++;
+    EXPECT_TRUE(AssertUkmReported("Event.ScrollBegin.Touch",
+                                  "TimeToScrollUpdateSwapBegin"));
     // Rappor metrics.
     EXPECT_TRUE(
         RapporSampleAssert("Event.Latency.ScrollUpdate.Touch."
@@ -511,8 +522,8 @@ TEST_F(RenderWidgetHostLatencyTrackerTest, TestTouchToFirstScrollHistograms) {
 
     ukm::TestUkmRecorder* test_ukm_recorder =
         test_browser_client_.GetTestUkmRecorder();
-    EXPECT_EQ(0U, test_ukm_recorder->sources_count());
-    EXPECT_EQ(0U, test_ukm_recorder->entries_count());
+    EXPECT_EQ(1U, test_ukm_recorder->sources_count());
+    EXPECT_EQ(total_ukm_entry_count, test_ukm_recorder->entries_count());
   }
 }
 

tools/metrics/ukm/ukm.xml

@@ -269,6 +269,40 @@ be describing additional metrics about the same event.
   </metric>
 </event>
 
+<event name="Event.ScrollBegin.Touch">
+  <owner>nzolghadr@chromium.org</owner>
+  <summary>
+    Metrics related to first scroll action caused by the generated ScrollUpdate
+    gesture event.
+  </summary>
+  <metric name="TimeToScrollUpdateSwapBegin">
+    <summary>
+      The time in microseconds between initial creation of a touch event and the
+      start of the frame swap on the GPU service caused by the generated
+      ScrollUpdate gesture event if that ScrollUpdate is the first such event in
+      a given scroll gesture event sequence. If no swap was induced by the
+      event, no recording is made.
+    </summary>
+  </metric>
+</event>
+
+<event name="Event.ScrollBegin.Wheel">
+  <owner>nzolghadr@chromium.org</owner>
+  <summary>
+    Metrics related to first scroll action caused by the generated ScrollUpdate
+    gesture event.
+  </summary>
+  <metric name="TimeToScrollUpdateSwapBegin">
+    <summary>
+      The time in microseconds between the initial creation of a wheel event and
+      the start of the frame swap on the GPU service caused by the generated
+      ScrollUpdate gesture event if that ScrollUpdate is the first such event in
+      a given scroll gesture event sequence. If no swap was induced by the
+      event, no recording is made.
+    </summary>
+  </metric>
+</event>
+
 <event name="Media.WatchTime">
   <owner>dalecurtis@chromium.org</owner>
   <summary>

ui/latency/latency_tracker.cc

@@ -159,6 +159,10 @@ void LatencyTracker::ComputeEndToEndLatencyHistograms(
                                   ".TimeToScrollUpdateSwapBegin2",
                               original_component, gpu_swap_begin_component);
 
+    ReportUkmScrollLatency("Event.ScrollBegin." + input_modality,
+                           "TimeToScrollUpdateSwapBegin", original_component,
+                           gpu_swap_begin_component);
+
     // TODO(lanwei): Will remove them when M56 is stable, see
     // https://crbug.com/669618.
     UMA_HISTOGRAM_INPUT_LATENCY_HIGH_RESOLUTION_MICROSECONDS(
@@ -179,6 +183,7 @@ void LatencyTracker::ComputeEndToEndLatencyHistograms(
       ReportRapporScrollLatency(
           "Event.Latency.ScrollUpdate.Touch.TimeToScrollUpdateSwapBegin2",
           original_component, gpu_swap_begin_component);
+
       ReportUkmScrollLatency("Event.ScrollUpdate.Touch",
                              "TimeToScrollUpdateSwapBegin", original_component,
                              gpu_swap_begin_component);