CacheExtensionConfig.addExtension() doesn't work

[tonyxu99]

For my use case, I want to cache "mp4" files. I use the following code:
CacheExtensionConfig extension = new CacheExtensionConfig();
extension.addExtension("mp4");
builder.setCacheExtensionConfig(extension);

However, the mp4 files still won't be cached. I have checked the source code (CacheExtensionConfig.java), this is the issue:
public boolean isMedia(String extension) {
if (TextUtils.isEmpty(extension)) {
return false;
}
if (NO_CACH.contains(extension)) {
return true;
}
return no_cache.contains(extension.toLowerCase().trim());
}
"mp4" is in NO_CACHE static HashSet. Therefore, there is no way to cache mp4 files even if we have added "mp4" to no_cashe
HashSet varible. I suggest that you should remove
if (NO_CACH.contains(extension)) {
return true;
}

Thank you.