Fix custom style not being applied to KickOffActivity progress dialogs (#589)

* Fix custom style not being applied to `KickOffActivity` progress dialogs

Signed-off-by: Alex Saveau <[email protected]>

* Use native `ContextThemeWrapper` instead

Signed-off-by: Alex Saveau <[email protected]>

Author: SUPERCILEX

auth/src/main/java/com/firebase/ui/auth/ui/FragmentHelper.java

@@ -6,6 +6,7 @@
 import android.os.Bundle;
 import android.support.annotation.RestrictTo;
 import android.support.v4.app.Fragment;
+import android.view.ContextThemeWrapper;
 
 @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
 public class FragmentHelper extends BaseHelper {
@@ -30,7 +31,9 @@ public void finish(int resultCode, Intent intent) {
     @Override
     public void showLoadingDialog(String message) {
         dismissDialog();
-        mProgressDialog = ProgressDialog.show(mFragment.getContext(), "", message, true);
+        ContextThemeWrapper context =
+                new ContextThemeWrapper(mFragment.getContext(), getFlowParams().themeId);
+        mProgressDialog = ProgressDialog.show(context, "", message, true);
     }
 
     public void startIntentSenderForResult(IntentSender sender, int requestCode)