Update a Slice Uri when unavailable

When a slice becomes unavailable, it should not update the
underlying data even if the view has not changed.

When we receive a change from an unavailable slice, notifychange
on the Uri and do not change the underlying data.

Change-Id: I91851ab668e4aece669fd65c14e0dc4ec2edefdf
Fixes: 77980406
Test: robotests

tests/robotests/src/com/android/settings/testutils/FakeUnavailablePreferenceController.java

@@ -0,0 +1,21 @@
+package com.android.settings.testutils;
+
+import android.content.Context;
+import android.provider.Settings;
+
+import com.android.settings.core.BasePreferenceController;
+
+public class FakeUnavailablePreferenceController extends BasePreferenceController {
+
+    public static final String AVAILABILITY_KEY = "fake_availability_key";
+
+    public FakeUnavailablePreferenceController(Context context) {
+        super(context, "key");
+    }
+
+    @Override
+    public int getAvailabilityStatus() {
+        return Settings.Global.getInt(mContext.getContentResolver(),
+                AVAILABILITY_KEY, 0);
+    }
+}