NIT lint warns fixed in BlobProvider (#39614)

Summary:
Pull Request resolved: #39614

NIT lint warns fixed in BlobProvider

changelog: [internal] internal

Reviewed By: christophpurrer

Differential Revision: D49483635

fbshipit-source-id: 51f6f0d7841d2552f30ed64d0bb4447bd0b0ec54

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/modules/blob/BlobProvider.java

@@ -27,7 +27,7 @@ public final class BlobProvider extends ContentProvider {
 
  private static final int PIPE_CAPACITY = 65536;
 
- private ExecutorService executor = Executors.newSingleThreadExecutor();
+ private final ExecutorService executor = Executors.newSingleThreadExecutor();
 
  @Override
  public boolean onCreate() {
@@ -61,7 +61,8 @@ public int update(Uri uri, ContentValues values, String selection, String[] sele
  }
 
  @Override
- public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundException {
+ public @Nullable ParcelFileDescriptor openFile(Uri uri, String mode)
+ throws FileNotFoundException {
  if (!mode.equals("r")) {
  throw new FileNotFoundException("Cannot open " + uri.toString() + " in mode '" + mode + "'");
  }
@@ -80,7 +81,7 @@ public ParcelFileDescriptor openFile(Uri uri, String mode) throws FileNotFoundEx
 
  final byte[] data = blobModule.resolve(uri);
  if (data == null) {
- throw new FileNotFoundException("Cannot open " + uri.toString() + ", blob not found.");
+ throw new FileNotFoundException("Cannot open " + uri + ", blob not found.");
  }
 
  ParcelFileDescriptor[] pipe;