In BlobGCJob::DoRunGC(), the `file_size` is always = 0.

[apple-ouyang]

In BlobGCJob::DoRunGC(), the file_size is always = 0.
I guess this variable is used to accumulate the file size of blob file.
Once the file_size >= blob_gc_->titan_cf_options().blob_file_target_size, Titan will create a new blob file right?
But there is no file_size += blob file size code.
So should we add some code or just delte the file_size?

[Connor1996]

Nice catch. Yes, the code is missing. Would you like to fix it?

[apple-ouyang]

yeah, I will try to make a PR

[apple-ouyang]

I have make a PR here #237