Log source with visibility change

- Add a method in VisibilityLoggerMixin to log visible event using
  LogMaker, which allows logging additional FIELD_CONTEXT field.
- In Utils.startFragment, add current page's metricsCategory as an extra
  to next page.
- In next page's onResume(), extract the previous page's metricsCategory
  and send it to VisibilityLoggerMixin.visible()
- Update all caller with additional paramters

Change-Id: I8e1f2597fa465b7d3aa16fa1d21c052a3219694a
Fix: 35359289
Test: RunSettingsRoboTests

src/com/android/settings/wifi/WifiSettings.java

@@ -850,8 +850,9 @@ public class WifiSettings extends RestrictedSettingsFragment
                 @Override
                 public void onClick() {
                     final SettingsActivity activity = (SettingsActivity) getActivity();
-                    activity.startPreferencePanel(ScanningSettings.class.getName(), null,
-                            R.string.location_scanning_screen_title, null, null, 0);
+                    activity.startPreferencePanel(WifiSettings.this,
+                            ScanningSettings.class.getName(),
+                            null, R.string.location_scanning_screen_title, null, null, 0);
                 }
             };
             mStatusMessagePreference.setText(