Ensure buffers are allocated to capacity for glBufferSubData.
Nevermind, glBufferSubData is way slower on iOS.

Apparently the driver can do clever things if you're recreating an
entire buffer rather than just updating a subsection. Updating a
previously used buffer can also mean waiting on the GPU to finish
rendering with it. Good to know!
JavaGL20.glBufferData shouldn't send the entire buffer.