Revert 282900 "Revert 282890 "[fsp] Add an option for mounting i..."

Revert 282900 "Revert 282890 "[fsp] Add an option for mounting i..."

Unable to reproduce locally even on a Debug build. Reverting the revert and
monitoring carefully.

> Revert 282890 "[fsp] Add an option for mounting in R/W mode."
> 
> > [fsp] Add an option for mounting in R/W mode.
> > 
> > Files app fetches information whether a volume is read only or R/W from
> > file_manager::VolumeManager, which used to always have the isReadOnly option
> > set to true for any provided file system.
> > 
> > However, since R/W operations are now under development, we should be able to
> > mark a volume as R/W.
> > 
> > In order to achieve that, a "writable" option has been added to the File System
> > Provider API mount() call. The argument is by default false, so file systems
> > are by default read only.
> > 
> > TEST=unit_test, browser_tests: *FileSystemProvider*Writable*
> > BUG=391362
> > 
> > Review URL: https://codereview.chromium.org/372163006
> 
> TBR=mtomasz@chromium.org
> 
> Review URL: https://codereview.chromium.org/391613002

TBR=mtomasz@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282908

[mtomasz, 2014-07-14 06:49:43]

Committed patchset #1 manually as r282908.