DO NOT MERGE: IDN: Fix handling of long domain names. We were incorrectly using sizeof() to calculate the size of the output array. Note that this change also changes the output size to 512 to minimize behavioural differences (especially wrt. ICU checks on sizes). bug: 30765246 Change-Id: I5d28ddc45d2d6d2bed3e479ca195ed2779b906ed (cherry picked from commit d00e7ed125b660ea562a331a9f98a31dfe13ca08)