ozone: Map TouchEvent::touch_id_ into expected range

ui/events/ozone/evdev/touch_event_converter_evdev.cc

Index: ui/events/ozone/evdev/touch_event_converter_evdev.cc
diff --git a/ui/events/ozone/evdev/touch_event_converter_evdev.cc b/ui/events/ozone/evdev/touch_event_converter_evdev.cc
index 95d0d77101ae69eb477db66ed934e98626dc8b18..9581373fa7bf2e81dcf3d03e743f74b52c874243 100644
--- a/ui/events/ozone/evdev/touch_event_converter_evdev.cc
+++ b/ui/events/ozone/evdev/touch_event_converter_evdev.cc
@@ -90,7 +90,8 @@ TouchEventConverterEvdev::TouchEventConverterEvdev(
       has_mt_(false),
       touch_points_(0),
       next_tracking_id_(0),
-      current_slot_(0) {
+      current_slot_(0),
+      touch_id_offset_(0) {
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kExtraTouchNoiseFiltering)) {
     touch_noise_finder_.reset(new TouchNoiseFinder);
@@ -198,6 +199,10 @@ int TouchEventConverterEvdev::GetTouchPoints() const {
   return touch_points_;
 }
 
+void TouchEventConverterEvdev::SetTouchIdOffset(int offset) {
+  touch_id_offset_ = offset;
+}
+
 void TouchEventConverterEvdev::OnFileCanReadWithoutBlocking(int fd) {
   input_event inputs[kNumTouchEvdevSlots * 6 + 1];
   ssize_t read_size = read(fd, inputs, sizeof(inputs));
@@ -357,10 +362,11 @@ EventType TouchEventConverterEvdev::GetEventTypeForTouch(
 void TouchEventConverterEvdev::ReportEvent(const InProgressTouchEvdev& event,
                                            EventType event_type,
                                            const base::TimeDelta& timestamp) {
-  dispatcher_->DispatchTouchEvent(TouchEventParams(
-      id_, event.slot, event_type, gfx::PointF(event.x, event.y),
-      gfx::Vector2dF(event.radius_x, event.radius_y), event.pressure,
-      timestamp));
+  dispatcher_->DispatchTouchEvent(
+      TouchEventParams(id_, touch_id_offset_ + event.slot, event_type,
+                       gfx::PointF(event.x, event.y),
+                       gfx::Vector2dF(event.radius_x, event.radius_y),
+                       event.pressure, timestamp));
 }
 
 void TouchEventConverterEvdev::ReportEvents(base::TimeDelta delta) {