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

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

Index: chrome/test/data/chromeos/gdata/delta_file_deleted_in_root.json
diff --git a/chrome/test/data/chromeos/gdata/delta_file_deleted_in_root.json b/chrome/test/data/chromeos/gdata/delta_file_deleted_in_root.json
index 3120d050f2ef9f4c20e96ff3d0f23a8f568d0e05..2a337382af85c11418afc52f9f5e773628cd3160 100644
--- a/chrome/test/data/chromeos/gdata/delta_file_deleted_in_root.json
+++ b/chrome/test/data/chromeos/gdata/delta_file_deleted_in_root.json
@@ -111,6 +111,10 @@
             "href": "https://changes/16683",
             "rel": "self",
             "type": "application/atom+xml"
+         }, {
+            "href": "https://fake_server/fake_root",
+            "rel": "http://schemas.google.com/docs/2007#parent",
+            "type": "application/atom+xml"
          } ],
          "published": {
             "$t": "2012-04-10T22:50:53.237Z"