libgestures_glue: Send MSC_TIMESTAMP if available

If an event from libevdev includes a MSC_TIMESTAMP field, send that
timestamp to the gesture library. This field will be used by the gesture
library because it has more accurate time deltas than CLOCK_MONOTONIC.

BUG=b:65041115
TEST=Tested manually on lux and eve, using CL:742488 and CL:938751.
MSC_TIMESTAMP is passed to gesture library if available.

Change-Id: I05e5a6615e10d33bd0e290b6bb8ff11c2f05f2fc
Reviewed-on: https://chromium-review.googlesource.com/817979Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Sean O'Brien <seobrien@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542190}

ui/events/ozone/evdev/libgestures_glue/gesture_interpreter_libevdev_cros.cc

@@ -211,6 +211,14 @@ void GestureInterpreterLibevdevCros::OnLibEvdevCrosEvent(Evdev* evdev,
     hwstate.buttons_down |= GESTURES_BUTTON_FORWARD;
   }
 
+  // Check if this event has an MSC_TIMESTAMP field
+  if (EvdevBitIsSet(evdev->info.msc_bitmask, MSC_TIMESTAMP)) {
+    hwstate.msc_timestamp = static_cast<stime_t>(Event_Get_Timestamp(evdev)) /
+                            base::Time::kMicrosecondsPerSecond;
+  } else {
+    hwstate.msc_timestamp = 0.0;
+  }
+
   GestureInterpreterPushHardwareState(interpreter_, &hwstate);
 }