Fix uninitialized timestamps being passed to the gesture lib

The CL corrects a bug where clock_gettime was placed in
a DCHECK call and thus not executed on release builds.

Contributed by sheckylin@chromium.org

BUG=chrome-os-partner:35111
TEST=samus ChromeOS build

Review URL: https://codereview.chromium.org/884313002

Cr-Commit-Position: refs/heads/master@{#313634}

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

@@ -29,7 +29,10 @@ struct GesturesTimer {
  private:
   void OnTimerExpired() {
     struct timespec ts;
-    DCHECK(!clock_gettime(CLOCK_MONOTONIC, &ts));
+    int fail = clock_gettime(CLOCK_MONOTONIC, &ts);
+    DCHECK(!fail);
+
+    // Run the callback and reschedule the next run if requested.
     stime_t next_delay = callback_(StimeFromTimespec(&ts), callback_data_);
     if (next_delay >= 0) {
       timer_.Start(FROM_HERE,