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

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

Index: chrome/test/data/chromeos/gdata/delta_file_added_in_directory.json
diff --git a/chrome/test/data/chromeos/gdata/delta_file_added_in_directory.json b/chrome/test/data/chromeos/gdata/delta_file_added_in_directory.json
index 7f2b9263285046dc61807fa012c87fa3f2cd6895..70babe7a0eedaa2e346aef97a004ec10dc76757f 100644
--- a/chrome/test/data/chromeos/gdata/delta_file_added_in_directory.json
+++ b/chrome/test/data/chromeos/gdata/delta_file_added_in_directory.json
@@ -193,6 +193,10 @@
             "href": "https://dir_1_self_link/folder:1_folder_resource_id",
             "rel": "edit",
             "type": "application/atom+xml"
+         }, {
+            "href": "https://fake_server/fake_root",
+            "rel": "http://schemas.google.com/docs/2007#parent",
+            "type": "application/atom+xml"
          } ],
          "published": {
             "$t": "2010-11-07T05:03:54.719Z"