Adds a "namespaces" option to the gadget definition, which takes a
list of namespace IDs. Enabled gadgets will only load when the
viewed page is in one of the required namespaces.
Bug: T204201
Bug: T63007
Change-Id: I7f797e35352b242ad78704074e98c6569a1adf91
The ResourceLoader module associated with the gadget will have
mobile and desktop targets, but this allows gadgets to disable
themselves on the mobile site if necessary by not adding the gadget
to the page if it's been marked as such.
This also has the benefit of not showing the gadget on the preferences
page if it's not relevant.
Bug: T328610
Change-Id: I4f2b57d1d22f641ff7520358a46cd0e6b2103aa9
Avoids expensive re-computations such as that of Action::getActionName, for
each gadget. It is now computed just once in the GadgetLoadConditions
constructor and stored.
This structure makes it cleaner to add more conditions down the line (such as
namespaces and content models - see T204201) and could be reused for user gadgets
(T36958).
Change-Id: I8cbc4bba4d248d9f2ff3a2836450f69970370b1a