This reverts to the previous behaviour before 8faf151.
Then, the InstalledAppProviderService would queue up a series of
changes, and only notify after 1 second of nothing being added to
the queue. This was good because CursorAdapters and LoaderManagers
would not continually requery the database several times a second (only
once at the end), but it meant there was a lag in the AppDetails screen
getting updated after installing/upgrading/deleting packages.
This restores that behaviour where general events (e.g. "some misc apps
in the database were changed") are "debounced" for 1 second. However it
also emits a more specific "package org.blah.com was changed" instantly.
In the long term, it would be good to remove any dependency on
ContentObservers and `notifyChange()` altogether, in preference of
either LocalBroadcastManager or RxJava. However this will depend on how
we go about changing the database layer in the future. The fact we now
depend on ContentProviders means that it would be a big change to move
away from LoaderManager + notifyChange().
Fixes#986.
a9d817441f