This adds a new API with the activity manager to find out about movement between
activities. For my sanity, the old IActivityWatcher is now renamed to
IActivityController, and the new activity movement interface is named
IActivityWatcher.
This changes the search manager itself to use the new API to manage its state.
Note that there are still problems when going back to the search dialog after
it was hidden -- the suggestions window no longer appears until you explicitly
dismiss and re-show it.
This also includes some changes to the window manager permission checks. Almost all of these
are to make it most testable (through an exception on a permission failure), though there is
one permission check that needed to be added: updateOrientationFromAppTokens().
