Fixed build when ProGuard is enabled

Summary: The interface needs to be public or ProGuard won't compile release builds.

Reviewed By: kirwan

Differential Revision: D5425151

fbshipit-source-id: 265324a57c663b6e483f7db69f33222ce46bbd0d

imagepipeline-base/src/main/java/com/facebook/cache/disk/DefaultDiskStorage.java

@@ -576,7 +576,7 @@ private FileInfo getShardFileInfo(File file) {
  FileType.CONTENT,
  FileType.TEMP,
  })
- private @interface FileType {
+ public @interface FileType {
  String CONTENT = CONTENT_FILE_EXTENSION;
  String TEMP = TEMP_FILE_EXTENSION;
  }