WIP: Plumbing input event latency reporting through Mus GPU.

ui/latency/latency_histogram_macros.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_LATENCY_LATENCY_HISTOGRAM_MACROS_H_
+#define UI_LATENCY_LATENCY_HISTOGRAM_MACROS_H_
+
+#include "base/metrics/histogram_functions.h"
+
+// Check valid timing for start and end latency components.
+#define CONFIRM_VALID_TIMING(start, end)     \
+  DCHECK(!start.first_event_time.is_null()); \
+  DCHECK(!end.last_event_time.is_null());    \
+  DCHECK_GE(end.last_event_time, start.first_event_time);
+
+// Event latency that is mostly under 1 second. We should only use 100 buckets
+// when needed.
+#define UMA_HISTOGRAM_INPUT_LATENCY_HIGH_RESOLUTION_MICROSECONDS(name, start, \
+                                                                 end)         \
+  CONFIRM_VALID_TIMING(start, end)                                            \
+  base::UmaHistogramCustomCounts(                                             \
+      name, (end.last_event_time - start.first_event_time).InMicroseconds(),  \
+      1, 1000000, 100);
+
+#define UMA_HISTOGRAM_INPUT_LATENCY_MILLISECONDS(name, start, end)           \
+  CONFIRM_VALID_TIMING(start, end)                                           \
+  base::UmaHistogramCustomCounts(                                            \
+      name, (end.last_event_time - start.first_event_time).InMilliseconds(), \
+      1, 1000, 50);
+
+// Long touch/wheel scroll latency component that is mostly under 200ms.
+#define UMA_HISTOGRAM_SCROLL_LATENCY_LONG_2(name, start, end)                 \
+  CONFIRM_VALID_TIMING(start, end)                                            \
+  base::Histogram::FactoryGet(name, 1000, 200000, 50,                         \
+                              base::HistogramBase::kUmaTargetedHistogramFlag) \
+      ->Add((end.last_event_time - start.first_event_time).InMicroseconds());
+
+// Short touch/wheel scroll latency component that is mostly under 50ms.
+#define UMA_HISTOGRAM_SCROLL_LATENCY_SHORT_2(name, start, end)                \
+  CONFIRM_VALID_TIMING(start, end)                                            \
+  base::Histogram::FactoryGet(name, 1, 50000, 50,                             \
+                              base::HistogramBase::kUmaTargetedHistogramFlag) \
+      ->Add((end.last_event_time - start.first_event_time).InMicroseconds());
+
+#endif  // UI_LATENCY_LATENCY_HISTOGRAM_MACROS_H_