Port Chromium OS touch noise filtering to Chromium

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..def0af898ca0f0c20a560b2d8c114250f3edc8cb
--- /dev/null
+++ b/ui/events/ozone/evdev/touch_noise/horizontally_aligned_touch_noise_filter.cc
@@ -0,0 +1,46 @@
+// 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 <cmath>
+
+#include "base/logging.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;
+      if (std::abs(other_touch.x - touch.x) <= kMaxDistance) {
+        VLOG(2) << base::StringPrintf(
+            "Cancel tracking id %d, down at %ld 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