Although, we don't need factory methods for DeleteRangeTransaction,
EditAggregateTransaction nor PlaceholderTransaction, for consistency with the
other transaction classes, they should have factory methods for making easier
to write the code.
For not making the performance slow down, they should be inline methods.
MozReview-Commit-ID: 7jl5yZNFYmP
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extra : rebase_source : 7cd5b5e268a670b3c8855407cc72dec12d34d8ff