I think the float array for orientation from native to Unity is not transferred the right way. I found this by:
1: Inserting the a log in the function call 'Cardboard_getPose' to print orientation values in the sdk
2: Building the sdk with log, and importing it in unity
3: Observing the orientation values at the unity side, on the device screen.

The orientation values from the native side (printed on log in xcode) does not match with values on unity side.
It has something to do with managed(Unity/c#) and unmanaged memory(c++) conversion. I have tried using GCHandle, Marshall. Not been able to solved so far.

@cai-mobfish
The issue is fixed. Changes are pushed to branch 'deviceOrientation'.

CACurrentMediaTime is iOS native method. Some other equivalent method in c# or unity is needed here.

On Android, the equivalent is written in util, with some extra calculation.

https://github.com/googlevr/cardboard/blob/master/hellocardboard-android/src/main/jni/util.cc

long GetMonotonicTimeNano() {
  struct timespec res;
  clock_gettime(CLOCK_MONOTONIC, &res);
  return (res.tv_sec * kNanosInSeconds) + res.tv_nsec;
}

iOS code:

  double targetTime = CACurrentMediaTime() * 1e9;
  targetTime += kPredictionTimeWithoutVsyncNanos;

Android code:

  long monotonic_time_nano = GetMonotonicTimeNano();
  monotonic_time_nano += kPredictionTimeWithoutVsyncNanos;

The goal is to have a monotonic time in nanoseconds.

Do a refactor, push the branch.

Done.