DataTransfer should have more 2 constructors. One takes |const nsAString&| and
sets its data to the string. The other takes |nsITransferable*| and stores only
its data with DataTransferItem.
If given data is external resource like the case of `HTMLEditor::PasteTransferable()`,
we should copy its data to each DataTransferItem because nsITransferable is not
cycle-collectable, but DataTransfer may be grabbed by JS. Unfortunately, adding
new path to initialize DataTransfer with nsITransferable instance is too risky
because DataTransfer and DataTransferItem work together to initialize each of
them if DataTransfer is in external mode. Therefore, this patch makes the
new constructor temporarily sets it to in external mode, then, cache usable types
first, then, call `FillAllExternalData()` to make each DataTransferItem initializes
its data by itself, finally, make the constructor set it to internal mode and release
nsITransferable instance. This is ugly implementation but the most reasonable
way for now because:
- We don't need to change DataTransfer nor DataTransferItem a lot in this bug.
- We don't need to duplicate any code like a loop in `CacheExternalData()`.
In another bug, we should redesign DataTransfer and DataTransferItem to
make DataTransferable easier to be added new constructors.
Differential Revision: https://phabricator.services.mozilla.com/D19298
--HG--
extra : moz-landing-system : lando
f8a317eb9a