Linux, Mac: Don't test parent directories when checking if a path is writable.
Linux, Mac: Don't test parent directories when checking if a path is writable.

This additional check has existed since the code was first written, but wtc
queried it in [1] and noted that it doesn't match the Windows version.

[1] http://codereview.chromium.org/541022/diff/1/3#newcode309

Removing this additional test doesn't break any unittests so it looks
like we can match the Windows code here.

http://codereview.chromium.org/545156

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@36760 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser