[Sync] Make SESSIONS an implicit type

net/tools/testserver/chromiumsync.py

Index: net/tools/testserver/chromiumsync.py
diff --git a/net/tools/testserver/chromiumsync.py b/net/tools/testserver/chromiumsync.py
index c4138bacf898f27d2882bb9665489c0232ced0dd..4a1eb9ae23616a88baef3562daa2c92bb252eae7 100644
--- a/net/tools/testserver/chromiumsync.py
+++ b/net/tools/testserver/chromiumsync.py
@@ -63,7 +63,8 @@ ALL_TYPES = (
     SYNCED_NOTIFICATION,
     THEME,
     TYPED_URL,
-    EXTENSION_SETTINGS) = range(20)
+    EXTENSION_SETTINGS,
+    TAB,) = range(21)
 
 # An eumeration on the frequency at which the server should send errors
 # to the client. This would be specified by the url that triggers the error.
@@ -99,6 +100,7 @@ SYNC_TYPE_TO_DESCRIPTOR = {
     SYNCED_NOTIFICATION: SYNC_TYPE_FIELDS["synced_notification"],
     THEME: SYNC_TYPE_FIELDS['theme'],
     TYPED_URL: SYNC_TYPE_FIELDS['typed_url'],
+    TAB: SYNC_TYPE_FIELDS['tab'],
     }
 
 # The parent ID used to indicate a top-level node.