Remove input metric ukm sampling

We added a sampling scheme when ukm was introduced
back in the day to control the amount of data we
report to the server.
Now that there is a general mechanism for controling
the data we can remove our own version of resampling
and rely only on the dashboard team to take care of
that.

Bug: 895463
Change-Id: If23332437205aa027b77a1140f28b9492692791a
Reviewed-on: https://chromium-review.googlesource.com/c/1283941Reviewed-by: Sahel Sharify <sahel@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Navid Zolghadr <nzolghadr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601247}

content/browser/renderer_host/input/render_widget_host_latency_tracker_unittest.cc

@@ -137,7 +137,6 @@ class RenderWidgetHostLatencyTrackerTest
     RenderViewHostImplTestHarness::SetUp();
     old_browser_client_ = SetBrowserClientForTesting(&test_browser_client_);
     tracker_ = std::make_unique<RenderWidgetHostLatencyTracker>(contents());
-    viz_tracker_.DisableMetricSamplingForTesting();
   }
 
   void TearDown() override {

ui/latency/latency_tracker.cc

@@ -106,10 +106,6 @@ void LatencyTracker::OnGpuSwapBuffersCompleted(const LatencyInfo& latency) {
   }
 }
 
-void LatencyTracker::DisableMetricSamplingForTesting() {
-  metric_sampling_ = false;
-}
-
 void LatencyTracker::ReportUkmScrollLatency(
     const InputMetricEvent& metric_event,
     base::TimeTicks start_timestamp,
@@ -121,11 +117,6 @@ void LatencyTracker::ReportUkmScrollLatency(
                             time_to_scroll_update_swap_begin_timestamp)
   CONFIRM_EVENT_TIMES_EXIST(start_timestamp, time_to_handled_timestamp)
 
-  // Only report a subset of this metric as the volume is too high.
-  if (metric_sampling_ &&
-      !sampling_scheme_[static_cast<int>(metric_event)].ShouldReport())
-    return;
-
   ukm::UkmRecorder* ukm_recorder = ukm::UkmRecorder::Get();
   if (ukm_source_id == ukm::kInvalidSourceId || !ukm_recorder)
     return;

ui/latency/latency_tracker.h

@@ -23,9 +23,6 @@ class LatencyTracker {
   void OnGpuSwapBuffersCompleted(const std::vector<LatencyInfo>& latency_info);
   void OnGpuSwapBuffersCompleted(const LatencyInfo& latency);
 
-  // Disables sampling of high volume metrics in unit tests.
-  void DisableMetricSamplingForTesting();
-
   using LatencyInfoProcessor =
       base::RepeatingCallback<void(const std::vector<ui::LatencyInfo>&)>;
   static void SetLatencyInfoProcessorForTesting(
@@ -54,39 +51,6 @@ class LatencyTracker {
       base::TimeTicks gpu_swap_end_timestamp,
       const LatencyInfo& latency);
 
-  typedef struct SamplingScheme {
-    SamplingScheme() : interval_(1), last_sample_(0) {}
-    SamplingScheme(int interval)
-        : interval_(interval), last_sample_(rand() % interval) {}
-    bool ShouldReport() {
-      last_sample_++;
-      last_sample_ %= interval_;
-      return last_sample_ == 0;
-    }
-
-   private:
-    int interval_;
-    int last_sample_;
-  } SamplingScheme;
-
-  // Whether the sampling is needed for high volume metrics. This will be off
-  // when we are in unit tests. This is a temporary field so we can come up with
-  // a more permanent solution for crbug.com/739169.
-  bool metric_sampling_ = true;
-
-  // The i'th member of this array stores the sampling rate for the i'th
-  // input metric event type. Initializing SamplingScheme with number X means
-  // that from every X events one will be reported. Note that the first event
-  // to report is also randomized.
-  SamplingScheme sampling_scheme_
-      [static_cast<int>(InputMetricEvent::INPUT_METRIC_EVENT_MAX) + 1] = {
-          SamplingScheme(5),   // SCROLL_BEGIN_TOUCH
-          SamplingScheme(50),  // SCROLL_UPDATE_TOUCH
-          SamplingScheme(5),   // SCROLL_BEGIN_WHEEL
-          SamplingScheme(2),   // SCROLL_UPDATE_WHEEL
-  };
-
-  DISALLOW_COPY_AND_ASSIGN(LatencyTracker);
 };
 
 }  // namespace latency