Replace internal AtomicFile usage with public API

Bug: 140590158
Test: m -j builds to confirm the public API isn't missing methods.
Test: Presubmit tests to verify no change in functionality
Change-Id: I3f0fb83689b9d742753f6cbbbc43d38947bc7b4d
diff --git a/services/core/java/com/android/server/wm/TaskSnapshotPersister.java b/services/core/java/com/android/server/wm/TaskSnapshotPersister.java
index 32a1d90..a156f5c 100644
--- a/services/core/java/com/android/server/wm/TaskSnapshotPersister.java
+++ b/services/core/java/com/android/server/wm/TaskSnapshotPersister.java
@@ -29,11 +29,11 @@
 import android.os.Process;
 import android.os.SystemClock;
 import android.util.ArraySet;
+import android.util.AtomicFile;
 import android.util.Slog;
 
 import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
-import com.android.internal.os.AtomicFile;
 import com.android.server.wm.nano.WindowManagerProtos.TaskSnapshotProto;
 
 import java.io.File;