[Sync] Make SESSIONS an implicit type

sync/protocol/sync.proto

Index: sync/protocol/sync.proto
diff --git a/sync/protocol/sync.proto b/sync/protocol/sync.proto
index 44dd59086e16e83dc32fbb47080a9c86ee163581..ed651136a02420978655070c8801fc9e30ec2560 100644
--- a/sync/protocol/sync.proto
+++ b/sync/protocol/sync.proto
@@ -366,8 +366,12 @@ message ChromiumExtensionsActivity {
 
 // Client specific configuration information.
 message ClientConfigParams {
-  // The set of data types this client has enabled.
+  // The set of data types this client has enabled (does not include proxy
+  // types).

[tim (not reviewing), 2013/02/09 01:23:59]

'does not include proxy types, as these don't have protocol field numbers.'
might be helpful to mention.

[Nicolas Zea, 2013/02/12 23:44:49]

Done.

  repeated int32 enabled_type_ids = 1;
+
+ // Whether the TABS proxy datatype is enabled on this client.
+ optional bool tabs_datatype_enabled = 2;

[Raz Mathias, 2013/02/09 01:33:48]

Please add a definition of "proxy type" to the proto here.  This comment
essentially becomes the reference point for the logs proto as well.

[Nicolas Zea, 2013/02/12 23:44:49]

Added to the comment above.

 };
 
 message CommitMessage {