ANR at android.os.MessageQueue.nativePollOnce

Question

We are seeing this ANR in different parts of our app. Wanted to understand what causes this ANR?

main (native): tid=1 systid=31940
#00 pc 0x5431c libc.so 
#01 pc 0x1313a5 libart.so 
#02 pc 0x2ab05b libart.so 
#03 pc 0x3659 libnativehelper.so 
#04 pc 0x9dee9 libandroid_runtime.so 
#05 pc 0x65c45 libgui.so 
#06 pc 0x11dcd libutils.so 
#07 pc 0x11abf libutils.so 
#08 pc 0xbcc7d libandroid_runtime.so 
       at android.os.MessageQueue.nativePollOnce(MessageQueue.java)
       at android.os.MessageQueue.next(MessageQueue.java:339)
       at android.os.Looper.loop(Looper.java:199)
       at android.app.ActivityThread.main(ActivityThread.java:8276)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:612)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1006)

This is what firebase has to say about this ANR -

This thread was idle when the ANR occurred. We don't have sufficient information to determine the root cause.