markGpuBegin method
Marks the beginning of GPU work.
Implementation
@override
void markGpuBegin(dynamic _) {
final q = _alloc();
if (q == null) return; // No free query this frame.
gl.glBeginQuery(angle.GL_TIME_ELAPSED_EXT, q);
_inFlight.addLast(q);
_beganThisFrame = true;
}