chromeos: make EventInjector reset time/latecy when injecting

This way telemetry only includes the time from ash, not the initial hop
from browser to ash.

BUG=759163
TEST=none

Change-Id: I65f514d6bee3346a7b828b431300e5cf3277d521
Reviewed-on: https://chromium-review.googlesource.com/c/1327416Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607320}

services/ws/event_injector.cc

@@ -133,6 +133,16 @@ void EventInjector::InjectEventNoAckImpl(int64_t display_id,
   if (!event_and_host.window_tree_host)
     return;
 
+  // Reset the latency time. This way telemetry doesn't include the time from
+  // browser to ash.
+  base::TimeTicks event_time = base::TimeTicks::Now();
+  ui::Event::DispatcherApi dispatcher_api(event_and_host.event.get());
+  dispatcher_api.set_time_stamp(event_time);
+  ui::LatencyInfo latency_info;
+  latency_info.AddLatencyNumberWithTimestamp(
+      ui::INPUT_EVENT_LATENCY_UI_COMPONENT, event_time, 1);
+  event_and_host.event->set_latency(latency_info);
+
   EventQueue::DispatchOrQueueEvent(window_service_,
                                    event_and_host.window_tree_host,
                                    event_and_host.event.get(), honor_rewriters);

ui/events/event.h

@@ -70,6 +70,7 @@ class EVENTS_EXPORT Event {
     void set_result(int result) {
       event_->result_ = static_cast<EventResult>(result);
     }
+    void set_time_stamp(base::TimeTicks time) { event_->time_stamp_ = time; }
 
    private:
     Event* event_;