In retrospect, I rushed the previous patch: we really need a way to tell
which deletion an ID belong to (and whether it was scheduled). So make
both result getters return an array with known keys that can be used
programmatically. Right now the class can only delete a single page, and
thus there's a single constant and this change is effectively a noop.
The deletionWasScheduled() method, introduced in 1.37, was
hard-deprecated out of an abundance of caution. There are no known uses
on codesearch, so it can probably just be removed in the next release.
Also reorder constructor params to DeletePage -- BacklinkCacheFactory is
a service injected by the factory, hence it shouldn't be grouped
together with value objects injected by the caller.
Change-Id: I32679b7cacc638ec3e9dc5b8dfe9bcc794b22ecf
