To make testing easier the defaults for the alternative string hashing were intentionally set to force enable the feature for a single build, 7u6b13. This was done by setting the enablement threshold to zero. For the release product and all other builds the threshold has always been planned to be 512. This patch adjusts the default to 512.
set the threshold default to 512
noreg-other because default change only. There is no visible mechanism to determine default being used.