Move migrateStartMetas pass after markTreeBuilderFixups pass

* This can potentially enable improved template wrapping in some
  odd edge cases.

* This change causes 6 selser failures (but which is actually a
  better serialization than the previous output).

Change-Id: I4fe332435c4d922feff989d6cda3f820a07e8106
Merge "Move migrateStartMetas pass after markTreeBuilderFixups pass"