Support account linking

app/src/main/AndroidManifest.xml

@@ -37,9 +37,6 @@
         <activity
             android:name=".auth.SignedInActivity"
             android:label="@string/title_auth_activity" />
-        <activity
-            android:name=".auth.AnonymousUpgradeActivity"
-            android:label="@string/title_anonymous_upgrade"/>
 
         <!-- Firestore demo -->
         <activity

app/src/main/java/com/firebase/uidemo/ChooserActivity.java

@@ -26,7 +26,6 @@
 import android.view.ViewGroup;
 import android.widget.TextView;
 
-import com.firebase.uidemo.auth.AnonymousUpgradeActivity;
 import com.firebase.uidemo.auth.AuthUiActivity;
 import com.firebase.uidemo.database.firestore.FirestoreChatActivity;
 import com.firebase.uidemo.database.firestore.FirestorePagingActivity;
@@ -54,7 +53,6 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
     private static class ActivityChooserAdapter extends RecyclerView.Adapter<ActivityStarterHolder> {
         private static final Class[] CLASSES = new Class[]{
                 AuthUiActivity.class,
-                AnonymousUpgradeActivity.class,
                 FirestoreChatActivity.class,
                 FirestorePagingActivity.class,
                 RealtimeDbChatActivity.class,
@@ -63,7 +61,6 @@ private static class ActivityChooserAdapter extends RecyclerView.Adapter<Activit
 
         private static final int[] DESCRIPTION_NAMES = new int[]{
                 R.string.title_auth_activity,
-                R.string.title_anonymous_upgrade,
                 R.string.title_firestore_activity,
                 R.string.title_firestore_paging_activity,
                 R.string.title_realtime_database_activity,
@@ -72,7 +69,6 @@ private static class ActivityChooserAdapter extends RecyclerView.Adapter<Activit
 
         private static final int[] DESCRIPTION_IDS = new int[]{
                 R.string.desc_auth,
-                R.string.desc_anonymous_upgrade,
                 R.string.desc_firestore,
                 R.string.desc_firestore_paging,
                 R.string.desc_realtime_database,