Verify that redacted MP4s are valid

Test: atest MediaStore_Video_MediaTest
Bug: 135499138
Change-Id: Icc77d8212e550d1d06ca577a3cb686d6ebd8653b
(cherry picked from commit 3f4327c646f68a62a7b28ac17e30084d54eed010)
diff --git a/tests/tests/provider/src/android/provider/cts/MediaStore_Video_MediaTest.java b/tests/tests/provider/src/android/provider/cts/MediaStore_Video_MediaTest.java
index fdf46ce..e30d604 100644
--- a/tests/tests/provider/src/android/provider/cts/MediaStore_Video_MediaTest.java
+++ b/tests/tests/provider/src/android/provider/cts/MediaStore_Video_MediaTest.java
@@ -31,6 +31,7 @@
 import android.content.ContentValues;
 import android.content.Context;
 import android.database.Cursor;
+import android.media.MediaExtractor;
 import android.media.MediaMetadataRetriever;
 import android.net.Uri;
 import android.os.ParcelFileDescriptor;
@@ -234,6 +235,7 @@
             mmr.setDataSource(pfd.getFileDescriptor());
             assertEquals("+37.4217-122.0834/",
                     mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_LOCATION));
+            assertEquals("2", mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_NUM_TRACKS));
         }
         try (InputStream in = mContentResolver.openInputStream(publishUri)) {
             byte[] bytes = FileUtils.readInputStreamFully(in);
@@ -256,6 +258,7 @@
             mmr.setDataSource(pfd.getFileDescriptor());
             assertEquals(null,
                     mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_LOCATION));
+            assertEquals("2", mmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_NUM_TRACKS));
         }
         try (InputStream in = mContentResolver.openInputStream(publishUri)) {
             byte[] bytes = FileUtils.readInputStreamFully(in);