There's even a comment in the test to indicate this.
The test file should replace all possible numbers with KEY_BLOCKS_UNUSED, but this was messed up in fixing the test case for Drizzle. This cset fixes that.
Currently tested on x86 and x86-64. Pretty sure (99.9%) that this will cover all platforms involved.
Our numbers are different from current MySQL 6 for some random reason that I don't really care about. Number of blocks * block_size roughly equals key cache size - so i'm happy.