Sync ui/events to chromium @ https://codereview.chromium.org/1210203002

ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc

Index: ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
diff --git a/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc b/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4123ffa601a4b93fed079ced4759c381fe137aee
--- /dev/null
+++ b/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
@@ -0,0 +1,56 @@
+// Copyright 2015 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.
+
+#include "ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.h"
+
+#include <inttypes.h>
+#include <cmath>
+
+#include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
+#include "base/strings/stringprintf.h"
+
+namespace ui {
+
+namespace {
+
+// The maximum horizontal distance between touches considered aligned.
+int kMaxDistance = 3;
+
+}  // namespace
+
+void HorizontallyAlignedTouchNoiseFilter::Filter(
+    const std::vector<InProgressTouchEvdev>& touches,
+    base::TimeDelta time,
+    std::bitset<kNumTouchEvdevSlots>* slots_with_noise) {
+  for (const InProgressTouchEvdev& touch : touches) {
+    // Only consider new touches.
+    if (!touch.touching || touch.was_touching)
+      continue;
+
+    // Check if within kMaxDistance of an existing touch.
+    for (const InProgressTouchEvdev& other_touch : touches) {
+      if (touch.slot == other_touch.slot || !other_touch.touching)
+        continue;
+
+      int distance = std::abs(other_touch.x - touch.x);
+
+      // Log |distance| to a UMA histogram to allow tuning of |kMaxDistance|.
+      UMA_HISTOGRAM_COUNTS_100(
+          "Ozone.TouchNoiseFilter.HorizontallyAlignedDistance", distance);
+
+      if (distance <= kMaxDistance) {
+        VLOG(2) << base::StringPrintf("Cancel tracking id %d, down at %" PRId64
+                                      " at %f,%f near touch %d at "
+                                      "%f,%f",
+                                      touch.tracking_id, time.ToInternalValue(),
+                                      touch.x, touch.y, other_touch.tracking_id,
+                                      other_touch.x, other_touch.y);
+        slots_with_noise->set(touch.slot);
+      }
+    }
+  }
+}
+
+}  // namespace ui