No media status is visible in Output Switcher

-Reflash header when get latest media controller

Bug: 152606491
Test: make -j42 RunSettingsRoboTests
Change-Id: I14542a7f8ba921c9d1dbaacf7e01c3ee673527b2

src/com/android/settings/panel/MediaOutputPanel.java

@@ -220,6 +220,7 @@ public class MediaOutputPanel implements PanelContent, LocalMediaManager.DeviceC
                 if (TextUtils.equals(controller.getPackageName(), mPackageName)) {
                     mMediaController = controller;
                     mMediaController.registerCallback(mCb);
+                    mCallback.onHeaderChanged();
                     break;
                 }
             }

tests/robotests/src/com/android/settings/panel/MediaOutputPanelTest.java

@@ -24,6 +24,7 @@ import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
@@ -58,6 +59,7 @@ import java.util.List;
 public class MediaOutputPanelTest {
 
     private static final String TEST_PACKAGENAME = "com.test.packagename";
+    private static final String TEST_PACKAGENAME2 = "com.test.packagename2";
     private static final String TEST_ARTIST = "test_artist";
     private static final String TEST_SONG = "test_song";
 
@@ -131,6 +133,21 @@ public class MediaOutputPanelTest {
         verify(mLocalMediaManager).startScan();
     }
 
+    @Test
+    public void onStart_activeSession_verifyOnHeaderChanged() {
+        mPanel.onStart();
+
+        verify(mCallback).onHeaderChanged();
+    }
+
+    @Test
+    public void onStart_noMatchedActiveSession_verifyNeverOnHeaderChanged() {
+        when(mMediaController.getPackageName()).thenReturn(TEST_PACKAGENAME2);
+        mPanel.onStart();
+
+        verify(mCallback, never()).onHeaderChanged();
+    }
+
     @Test
     public void onStop_shouldUnregisterCallback() {
         mPanel.onStop();
@@ -255,12 +272,13 @@ public class MediaOutputPanelTest {
     @Test
     public void onMetadataChanged_verifyCallOnHeaderChanged() {
         mPanel.onStart();
+        verify(mCallback).onHeaderChanged();
         verify(mMediaController).registerCallback(mControllerCbs.capture());
         final MediaController.Callback controllerCallbacks = mControllerCbs.getValue();
 
         controllerCallbacks.onMetadataChanged(mMediaMetadata);
 
-        verify(mCallback).onHeaderChanged();
+        verify(mCallback, times(2)).onHeaderChanged();
     }
 
     @Test