If you open AppDetails, initiate a download + install, and then navigate
away, it still pops open the install dialog for you. This is because it
never deregisters the broadcast receiver.
This change maintains the behaviour of always having the broadcast
receiver. This is because it is only added when the download
completes, and would require further refactoring to change that.
Instead, we listen for the receiver, but we ask if the AppDetails view
for the apk in question is actually visible to the user. If not, we
don't try to initiate the package manager.
8a69816648