Fix chrome upload with content uri

For android, the upload file dialog returns files with content uri scheme(content://).
This CL makes it possible for upload to work with this new file type.
It fixes both the form and fileapi based uploads.

The CL follows the same code path used by regular file upload and the content url is encompassed by a FilePath object.

R=jar@chromium.org, joth@chromium.org, kinuko@chromium.org, mmenke@chromium.org, tsepez@chromium.org
TBR=yfriedman
BUG=278640

Review URL: https://codereview.chromium.org/46303005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235752 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235752