Create ProxyConfigService on IOS in remoting/base/url_request_context.cc

Review URL: https://codereview.chromium.org/92823003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237726 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237726