Fix the problem that when the MainSwitchPreference is gone,

there will be a blank area.

- Disable the visibility of preference when the the hide() method
  is invoked.

Fix: 192332931
Test: robotest and see the UI
Change-Id: Iec5a06ca689843ebb692b1b7040f1d2be9f45bc2

tests/robotests/src/com/android/settings/widget/SettingsMainSwitchPreferenceTest.java

@@ -76,6 +76,7 @@ public class SettingsMainSwitchPreferenceTest {
         mPreference.onBindViewHolder(mHolder);
 
         assertThat(mPreference.isShowing()).isTrue();
+        assertThat(mPreference.isVisible()).isTrue();
     }
 
     @Test
@@ -85,5 +86,6 @@ public class SettingsMainSwitchPreferenceTest {
         mPreference.onBindViewHolder(mHolder);
 
         assertThat(mPreference.isShowing()).isFalse();
+        assertThat(mPreference.isVisible()).isFalse();
     }
 }