Fix issue #7649590: Background windows sometimes not being hidden for secondary users

There are two things going on here:

(1) In secondary users, some times theme information such as whether
the window is full screen opaque was not being retrieved, so the window
manager didn't know that it could hide the windows behind the app.
This would just be a performance problem, except that:

(2) There appear to be a number of applications that declare that they
are full screen opaque, when in fact they are not.  Instead they are
using window surfaces with an alpha channel, and setting some pixels
in their window to a non-opaque alpha level.  This will allow you to
see whatever is behind the app.  If the system happens to completely
remove the windows behind the app, and somebody is filling the frame
buffer with black, then you will see what the app intends -- those
parts of its UI blended with black.  If one of those cases doesn't
hold (and though we have never guaranteed they would, in practice this
is generally what happens), then you will see something else.

At any rate, if nothing else than for performance reasons, we need to
fix issue #1.

It turns out what is happening here is that the AttributeCache used
by the activity manager and window manager to retreive theme and other
information about applications has not yet been updated for multi-user.

One of the things we retrieve from this is the theme information telling
the window manager whether an application's window should be treated
as full screen opaque, allowing it to hide any windows behind it.  In
the current implementation, the AttributeCache always retrieves this
information about the application as the primary user (user 0).

So, if you have an application that is installed on a secondary user but
not installed on the primary user, when the AttributeCache tries to retrieve
the requested information for it, then from the perspective of the primary user
it considers the application not installed, and is not able to retrieve that

The change here makes AttributeCache multi-user aware, keeping all of its
data separately per-user, and requiring that callers now provide the user
they want to retrieve information for.  Activity manager and window manager
are updated to be able to pass in the user when needed.  This required some
fiddling of the window manager to have that information available -- in
particular it needs to be associated with the AppWindowToken.

Change-Id: I4b50b4b3a41bab9d4689e61f3584778e451343c8
10 files changed