Permission to view shared storage for all users.

Typical apps are restricted so they can only view shared storage
belonging to the user they're running as.  However, a handful of
system components need access to shared storage across all users,
such as DefaultContainerService and SystemUI.

Since WRITE_MEDIA_STORAGE already offers this functionality by
bypassing any FUSE emulation, reuse it to grant the "sdcard_rw" GID
which is no longer handed out to third-party apps.  Then we change
the FUSE daemon to allow the "sdcard_rw" GID to see shared storage
of all users.

Bug: 19995822
Change-Id: I504c2a179ba74f142ed0d32da5baa69f4212cd82
diff --git a/packages/SystemUI/AndroidManifest.xml b/packages/SystemUI/AndroidManifest.xml
index 7c56d63..ea032b3 100644
--- a/packages/SystemUI/AndroidManifest.xml
+++ b/packages/SystemUI/AndroidManifest.xml
@@ -25,7 +25,8 @@
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
-    <uses-permission android:name="android.permission.ACCESS_ALL_EXTERNAL_STORAGE" />
+    <!-- Used to read storage for all users -->
+    <uses-permission android:name="android.permission.WRITE_MEDIA_STORAGE" />
     <uses-permission android:name="android.permission.WAKE_LOCK" />
 
     <uses-permission android:name="android.permission.INJECT_EVENTS" />