Use trampoline for FaceEnrollIntroductionInternal

This gives activity embedding logic a chance to notice what taskfragment
the elements should be in, and prevents a bug where the topmost activity
can dissapear under the stack.

Test: Manual
Bug: 324018644
Change-Id: Iea8d367247b13ffe66f4558be49e8060fb7db4c5

src/com/android/settings/biometrics/face/FaceEnrollIntroductionInternal.java

@@ -16,8 +16,34 @@
 
 package com.android.settings.biometrics.face;
 
+import static com.android.settings.Utils.SETTINGS_PACKAGE_NAME;
+
+import android.content.Intent;
+import android.os.Bundle;
+
+import androidx.fragment.app.FragmentActivity;
+
 /**
  * Wrapper of {@link FaceEnrollIntroduction} to use with a pre-defined task affinity.
+ *
+ * <p>Trampolines over to FaceEnrollIntroduction - doing this as a trampoline rather than having
+ * this activity extend FaceEnrollIntroduction works around b/331157120.
  */
-public class FaceEnrollIntroductionInternal extends FaceEnrollIntroduction {
+public class FaceEnrollIntroductionInternal extends FragmentActivity {
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        if (isFinishing()) {
+            return;
+        }
+
+        // Copy our intent to grab all extras. Drop flags so we don't start new tasks twice.
+        Intent trampoline = new Intent(getIntent());
+        trampoline.setFlags(0);
+
+        // Trampoline to the intended activity, and finish
+        trampoline.setClassName(SETTINGS_PACKAGE_NAME, FaceEnrollIntroduction.class.getName());
+        startActivity(trampoline);
+        finish();
+    }
 }