drive: Add showroot=true to WAPI feed URLs and ignore "no parent" entries.

chrome/test/data/chromeos/gdata/uploaded_file.json

 {
    "encoding": "UTF-8",
    "entry": {
       "app$edited": {
          "$t": "2012-01-02T00:11:22.330Z",
          "xmlns$app": "http://www.w3.org/2007/app"
       },
       "author": [ {
          "email": {
             "$t": "tester@testing.com"
@@ skipping 61 matching lines @@
          "rel": "self",
          "type": "application/atom+xml"
       }, {
          "href": "https://file1_link_self/file:remote_file_id",
          "rel": "edit",
          "type": "application/atom+xml"
       }, {
          "href": "https://file_edit_media",
          "rel": "edit-media",
          "type": "audio/mpeg"
-      } ],
+      }, {
+            "href": "https://fake_server/fake_root",
+            "rel": "http://schemas.google.com/docs/2007#parent",
+            "type": "application/atom+xml"
+         } ],
       "published": {
          "$t": "2012-01-02T00:11:22.330Z"
       },
       "title": {
          "$t": "remote.txt"
       },
       "updated": {
          "$t": "2012-01-02T00:11:22.330Z"
       },
       "xmlns": "http://www.w3.org/2005/Atom",
       "xmlns$batch": "http://schemas.google.com/gdata/batch",
       "xmlns$docs": "http://schemas.google.com/docs/2007",
       "xmlns$gd": "http://schemas.google.com/g/2005",
       "xmlns$openSearch": "http://a9.com/-/spec/opensearch/1.1/"
    },
    "version": "1.0"
 }