Revert 282890 "[fsp] Add an option for mounting in R/W mode."

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

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=282900

[mtomasz, 2014-07-14 04:02:25]

Committed patchset #1 manually as r282900 (tree was closed).