In adventure mode, ender pearls can not be placed in end portal frames. This is good, because it works with the new adventure mode system. I expected the NBT tag CanPlaceOn to allow it to be placed, yet it did not work.

I used the following command:
/give @p ender_eye 1 0

This seems rather important to any map maker who wishes to utilize the function of putting ender eyes in end portal frames in adventure mode.

Creative mode and Survival mode still work normally.