fix time point convert issue (move from mac branch)

com.unity.uiwidgets/Runtime/async2/timer.cs

             cancel();
         }
 
-        public abstract int tick { get; }
+        public abstract long tick { get; }
 
         public abstract bool isActive { get; }
 
     }
 
     class _Timer : Timer {
-        int _tick = 0;
+        long _tick = 0;
-        int _wakeupTime;
+        long _wakeupTime;
-        _Timer(ZoneUnaryCallback callback, int wakeupTime, int milliSeconds, bool repeating) {
+        _Timer(ZoneUnaryCallback callback, long wakeupTime, int milliSeconds, bool repeating) {
             _callback = callback;
             _wakeupTime = wakeupTime;
             _milliSeconds = milliSeconds;
                 milliSeconds = 0;
             }
 
-            int now = UIMonoState_timerMillisecondClock();
-            int wakeupTime = (milliSeconds == 0) ? now : (now + 1 + milliSeconds);
+            long now = UIMonoState_timerMillisecondClock();
+            long wakeupTime = (milliSeconds == 0) ? now : (now + 1 + milliSeconds);
 
             _Timer timer = new _Timer(callback, wakeupTime, milliSeconds, repeating);
             timer._enqueue();
 
         public override bool isActive => _callback != null;
 
-        public override int tick => _tick;
+        public override long tick => _tick;
 
         void _advanceWakeupTime() {
             if (_milliSeconds > 0) {
         void _enqueue() {
             Isolate.ensureExists();
             
-            GCHandle callabackHandle = GCHandle.Alloc(this);
-            UIMonoState_postTaskForTime(_postTaskForTime, (IntPtr) callabackHandle, _wakeupTime * MILLI_TO_NANO);
+            GCHandle callbackHandle = GCHandle.Alloc(this);
+            UIMonoState_postTaskForTime(_postTaskForTime, (IntPtr) callbackHandle, _wakeupTime * MILLI_TO_NANO);
         }
 
         [MonoPInvokeCallback(typeof(UIMonoState_postTaskForTimeCallback))]
                     }
                     else if (timer._milliSeconds > 0) {
                         var ms = timer._milliSeconds;
-                        int overdue = UIMonoState_timerMillisecondClock() - timer._wakeupTime;
+                        long overdue = UIMonoState_timerMillisecondClock() - timer._wakeupTime;
-                            int missedTicks = overdue / ms;
+                            long missedTicks = overdue / ms;
                             timer._wakeupTime += missedTicks * ms;
                             timer._tick += missedTicks;
                         }
         }
 
         [DllImport(NativeBindings.dllName)]
-        static extern int UIMonoState_timerMillisecondClock();
+        static extern long UIMonoState_timerMillisecondClock();
 
         delegate void UIMonoState_postTaskForTimeCallback(IntPtr callbackHandle);
 

engine/src/lib/ui/ui_mono_state.cc

           fml::TimeDelta::FromNanoseconds(target_time_nanos)));
 }
 
-UIWIDGETS_API(int)
+UIWIDGETS_API(int64_t)
 UIMonoState_timerMillisecondClock() { return Mono_TimelineGetMicros() / 1000; }
 
 }  // namespace uiwidgets