This patch refactors the serialization of MemProf data to a switch
statement style:
switch (Version) {
case Version0:
return ...;
case Version1:
return ...;
}
just like IndexedMemProfRecord::serialize.
A reasonable amount of code is shared and factored out to helper
functions between writeMemProfV0 and writeMemProfV1 to the extent that
doens't hamper readability.