[Retry] PPAPI: Add new PPB_FileRef.MakeDirectory to support exclusive operation

Original Review: https://codereview.chromium.org/113363004/

Current PPB_FileRef.MakeDirectory returns PP_OK if a directory exists on
the given path. This makes it difficult to create POSIX compatible API on
top of PPAPI.

This change introduces new PPB_FileRef.MakeDirectory as dev channel API.
That makes a new directory according to the given PP_MakeDirectoryFlags
values. The flags provide exclusive operation option. If exclusive flag
is specified and a directory exists on the given path, the function fails
and returns PP_ERROR_FILEEXISTS.


BUG=314879
TEST=browser_tests
TBR=dmichael@chromium.org,yzshen@chromium.org,tsepez@chromium.org

Review URL: https://codereview.chromium.org/131403004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244148 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 244148