Fix videoPreference is broken when switch to multiple window

Fixes: 117802997
Test: robolectric, switch between multiple window and single window.
The video should keep displaying.

Change-Id: I97b6a4516b2591b80d9a046809ce4090fb02c80f

src/com/android/settings/gestures/AssistGestureSettingsPreferenceController.java

@@ -68,7 +68,7 @@ public class AssistGestureSettingsPreferenceController extends GesturePreference
     }
 
     @Override
-    public void onResume() {
+    public void onStart() {
         if (mWasAvailable != isAvailable()) {
             // Only update the preference visibility if the availability has changed -- otherwise
             // the preference may be incorrectly added to screens with collapsed sections.