Fix bug 837: realloc mode info buffers on resize

The test to determine if the mode info buffers need
to be resized when the frame size changes was
incorrect, as per bug 837.

By storing the size of the allocated data structure,
a simple test determines whether to allocate more
memory when the frame size changes.

Change-Id: I1544698f2882cf958fc672485614f2f46e9719bd