Correctly esapce destination file name in fileBrowserPrivate.startCopy.

BUG=345949

Review URL: https://codereview.chromium.org/176703003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252899 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252899