[Sync] Log age of auth tokens on authentication failure

sync/engine/net/server_connection_manager.h

Index: sync/engine/net/server_connection_manager.h
diff --git a/sync/engine/net/server_connection_manager.h b/sync/engine/net/server_connection_manager.h
index 917d5b427c699a4ad29bf52095cc90eda68a9767..76609f984136f8ead5ffd383a3e81a6ec09b1e05 100644
--- a/sync/engine/net/server_connection_manager.h
+++ b/sync/engine/net/server_connection_manager.h
@@ -225,10 +225,12 @@ class SYNC_EXPORT_PRIVATE ServerConnectionManager {
   }
 
   // Returns true if the auth token is succesfully set and false otherwise.
-  bool set_auth_token(const std::string& auth_token) {
+  bool set_auth_token(const std::string& auth_token,

[tim (not reviewing), 2013/05/03 00:46:43]

This method should be renamed as per style guide (SetAuthTokenAndTime?), also
comment the new parameter and how it should relate to auth_token.

[Nicolas Zea, 2013/05/03 01:31:41]

Done.

+                      const base::Time& auth_token_time) {
     DCHECK(thread_checker_.CalledOnValidThread());
     if (previously_invalidated_token != auth_token) {
       auth_token_.assign(auth_token);
+      auth_token_time_ = auth_token_time;
       previously_invalidated_token = std::string();
       return true;
     }
@@ -299,6 +301,10 @@ class SYNC_EXPORT_PRIVATE ServerConnectionManager {
   // The auth token to use in authenticated requests.
   std::string auth_token_;
 
+  // The time at which this auth token was last created/refreshed.
+  // Used for histogramming.
+  base::Time auth_token_time_;
+
   // The previous auth token that is invalid now.
   std::string previously_invalidated_token;