Update all preferences when the account preference updates UI

When an account is added or removed, the account preference controller
just updates the account list, whereas there's no trigger point for the
account data sync preferences to refresh.

Add an API to update all preferences in DashboardFragment, so we can
refresh the account sync preferences whenever the account list is
updated.

Bug: 185479221
Test: robotest, manual
Change-Id: Ide3d972abae09ce0175e3bafbb1f4a5e307d20c8

src/com/android/settings/dashboard/DashboardFragment.java

@@ -415,6 +415,30 @@ public abstract class DashboardFragment extends SettingsPreferenceFragment
         updatePreferenceVisibility(mPreferenceControllers);
     }
 
+    /**
+     * Force update all the preferences in this fragment.
+     */
+    public void forceUpdatePreferences() {
+        final PreferenceScreen screen = getPreferenceScreen();
+        if (screen == null || mPreferenceControllers == null) {
+            return;
+        }
+        for (List<AbstractPreferenceController> controllerList : mPreferenceControllers.values()) {
+            for (AbstractPreferenceController controller : controllerList) {
+                final String key = controller.getPreferenceKey();
+                final Preference preference = findPreference(key);
+                if (preference == null) {
+                    continue;
+                }
+                final boolean available = controller.isAvailable();
+                if (available) {
+                    controller.updateState(preference);
+                }
+                preference.setVisible(available);
+            }
+        }
+    }
+
     @VisibleForTesting
     void updatePreferenceVisibility(
             Map<Class, List<AbstractPreferenceController>> preferenceControllers) {