Summary:
gcc-4.8 returns error when using the constructor. Not sure if it's a compiler bug/limitation or code issue:
```
table/block_based/block_based_table_reader.cc:3183:67: error: use of deleted function ‘rocksdb::WritableFileStringStreamAdapter::WritableFileStringStreamAdapter(rocksdb::WritableFileStringStreamAdapter&&)’
```
Pull Request resolved: https://github.com/facebook/rocksdb/pull/7358
Reviewed By: pdillinger
Differential Revision: D23577651
Pulled By: jay-zhuang
fbshipit-source-id: b0197e3d3538da61a6f3866410d88d2047fb9695