Log visibility change for all fragments.

Bug: 30681771
Test: SettingsUnitTests

Refactor visibility logging from InstrumentedFragment into a mixin. And
apply mixin in remaining fragments.

Change-Id: Ibbb59904336254a3e4bb9e8c7d0b36e5a6bc2622

src/com/android/settings/display/NightDisplaySettings.java

@@ -200,7 +200,7 @@ public class NightDisplaySettings extends SettingsPreferenceFragment
     }
 
     @Override
-    protected int getMetricsCategory() {
+    public int getMetricsCategory() {
         return MetricsEvent.NIGHT_DISPLAY_SETTINGS;
     }
 }

src/com/android/settings/display/ScreenZoomPreferenceFragmentForSetupWizard.java

@@ -23,7 +23,7 @@ public class ScreenZoomPreferenceFragmentForSetupWizard
         extends ScreenZoomSettings {
 
     @Override
-    protected int getMetricsCategory() {
+    public int getMetricsCategory() {
         return MetricsEvent.SUW_ACCESSIBILITY_DISPLAY_SIZE;
     }
 

src/com/android/settings/display/ScreenZoomSettings.java

@@ -94,7 +94,7 @@ public class ScreenZoomSettings extends PreviewSeekBarPreferenceFragment impleme
     }
 
     @Override
-    protected int getMetricsCategory() {
+    public int getMetricsCategory() {
         return MetricsEvent.DISPLAY_SCREEN_ZOOM;
     }