Add the navigation redirect-chain to Sync sessions proto for offline analysis.

sync/protocol/session_specifics.proto

Index: sync/protocol/session_specifics.proto
diff --git a/sync/protocol/session_specifics.proto b/sync/protocol/session_specifics.proto
index 3de3e1478ab6aa6ba1ee096c89121bcd9b82f827..fea5450a5c6d3b95f59c40582d75c66a4261440a 100644
--- a/sync/protocol/session_specifics.proto
+++ b/sync/protocol/session_specifics.proto
@@ -136,4 +136,17 @@ message TabNavigation {
   optional int32 http_status_code = 20;
   // Referrer policy.
   optional int32 referrer_policy = 21;
+  // The redirections traversed during this navigation.
+  // The first entry corresponds to the original URL, and the last entry 
+  // corresponds the last URL that redirected (to the virtual_url).
+  repeated NavigationRedirect navigation_redirect = 22;
+  // Normally not present.
+  // The last URL traversed when different from the virtual_url.
+  optional string last_navigation_redirect_url = 23;

[haitaol1, 2014/01/17 23:52:23]

Can you confirm that this could happen, i.e. virtual_url is different from last
url in redirect chain?

[Donn Denman, 2014/01/18 01:30:19]

I have only seen this for urls like the new tab page.  I don't know if it would
every happen with redirection, but I was thinking it would be good to capture
the data in the case where it is different, so we would know.  Alternatively, we
could just remove this field.

+}
+
+// Navigation information for a single redirection within a single navigation.
+message NavigationRedirect {
+  // A URL that redirected while navigating to this virtual_url.
+  optional string url = 1;
 }