[Sync] Update session protos.

chrome/browser/sync/protocol/session_specifics.proto

Index: chrome/browser/sync/protocol/session_specifics.proto
diff --git a/chrome/browser/sync/protocol/session_specifics.proto b/chrome/browser/sync/protocol/session_specifics.proto
index 28ffbd99c650564318bb83b11465b7c23750f1ed..7414771b14ab1d80cf2d0c9e19fdd5540837988d 100644
--- a/chrome/browser/sync/protocol/session_specifics.proto
+++ b/chrome/browser/sync/protocol/session_specifics.proto
@@ -20,12 +20,20 @@ message SessionSpecifics {
   // Unique id for the client.
   optional string session_tag = 1;
   optional SessionHeader header = 2;
-  optional SessionTab tab = 3;  
+  optional SessionTab tab = 3;
 }
 // Properties of session sync objects.
 message SessionHeader {
   // Each session is composed of windows.
   repeated SessionWindow window = 2;
+  // A non-unique but human-readable name to describe this client.
+  optional string client_name = 3;
+  // The type of device.
+  enum DeviceType {
+    TYPE_PC = 1;
+    TYPE_CROS = 2;
+  }
+  optional DeviceType device_type = 4;
 }
 message SessionWindow {
   // Unique (to the owner) id for this window.