[FileSystem] Fix ConvertFrom() base64 decode algorithm
[FileSystem] Fix ConvertFrom() base64 decode algorithm

fixed by: Leandro A. F. Pereira

hgl888/tizen-extensions-crosswalk,paritosh-in/tizen-extensions-crosswalk,hgl888/tizen-extensions-crosswalk,pk-sam/tizen-extensions-crosswalk,paritosh-in/tizen-extensions-crosswalk,hgl888/tizen-extensions-crosswalk,pk-sam/tizen-extensions-crosswalk,hgl888/tizen-extensions-crosswalk,pk-sam/tizen-extensions-crosswalk,pk-sam/tizen-extensions-crosswalk,crosswalk-project/tizen-extensions-crosswalk,pk-sam/tizen-extensions-crosswalk,hgl888/tizen-extensions-crosswalk,paritosh-in/tizen-extensions-crosswalk,pk-sam/tizen-extensions-crosswalk,paritosh-in/tizen-extensions-crosswalk,crosswalk-project/tizen-extensions-crosswalk,paritosh-in/tizen-extensions-crosswalk,crosswalk-project/tizen-extensions-crosswalk,crosswalk-project/tizen-extensions-crosswalk,hgl888/tizen-extensions-crosswalk,crosswalk-project/tizen-extensions-crosswalk,paritosh-in/tizen-extensions-crosswalk,crosswalk-project/tizen-extensions-crosswalk