Add lifecycle observers for future mixin structures.

- Converted VisibilityLoggerMixin into a LifecyclerObservable so we
  don't have to call logger.onResume/onPause manually in most fragments.
- Observable will be useful when we provide logics across all
  fragment/activity, eg log lifecycle event latencies.
- Also added new tests for lifecycle component.

Bug: 30681529
Test: RunSettingsRoboTests

Change-Id: Ida39300aeb42f71b2e0bbfaebd0c51dc468cb5e8

src/com/android/settings/ZonePicker.java

@@ -58,7 +58,8 @@ public class ZonePicker extends ListFragment implements Instrumentable {
 
     private static final int MENU_TIMEZONE = Menu.FIRST+1;
     private static final int MENU_ALPHABETICAL = Menu.FIRST;
-    private final VisibilityLoggerMixin mVisibilityLoggerMixin = new VisibilityLoggerMixin(this);
+    private final VisibilityLoggerMixin mVisibilityLoggerMixin =
+            new VisibilityLoggerMixin(getMetricsCategory());
 
     private boolean mSortedByTimezone;
 
@@ -185,7 +186,7 @@ public class ZonePicker extends ListFragment implements Instrumentable {
     @Override
     public void onResume() {
         super.onResume();
-        mVisibilityLoggerMixin.onResume(getActivity());
+        mVisibilityLoggerMixin.onResume();
     }
 
     @Override
@@ -242,7 +243,7 @@ public class ZonePicker extends ListFragment implements Instrumentable {
     @Override
     public void onPause() {
         super.onPause();
-        mVisibilityLoggerMixin.onPause(getActivity());
+        mVisibilityLoggerMixin.onPause();
     }
 
     private static class MyComparator implements Comparator<Map<?, ?>> {