Hide overlays over uninstall confirm dialog

Test: atest CtsPackageUninstallTestCases
Fixes: 171221302
Change-Id: I38b6d85871064d76f2911e20acc74b4ab76406b3

packages/PackageInstaller/src/com/android/packageinstaller/UninstallerActivity.java

@@ -17,6 +17,7 @@
 package com.android.packageinstaller;
 
 import static android.app.AppOpsManager.MODE_ALLOWED;
+import static android.view.WindowManager.LayoutParams.SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
 
 import static com.android.packageinstaller.PackageUtil.getMaxTargetSdkVersionForUid;
 
@@ -87,6 +88,8 @@ public class UninstallerActivity extends Activity {
 
     @Override
     public void onCreate(Bundle icicle) {
+        getWindow().addSystemFlags(SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
+
         // Never restore any state, esp. never create any fragments. The data in the fragment might
         // be stale, if e.g. the app was uninstalled while the activity was destroyed.
         super.onCreate(null);