Bug 807883: Update NSPR to NSPR 4.9.6 Beta 2. This adds 'const' to the
'pool' input parameter of PL_SizeOfArenaPoolExcludingPool. r=n.nethercote.
Merge bug 807883.
Bug 817395 - Clean up the temporary style context used for font size comparision of the root before the rule node tree is rebuilt. r=dbaron