Add histograms to entire MergeSession flow.

google_apis/gaia/ubertoken_fetcher.cc

Index: google_apis/gaia/ubertoken_fetcher.cc
diff --git a/google_apis/gaia/ubertoken_fetcher.cc b/google_apis/gaia/ubertoken_fetcher.cc
index 15e5932bed620498fe8ede7fc2cd6ad2369c987d..8fa330fc962c85bbae8fd159b2b5e5eb138f695f 100644
--- a/google_apis/gaia/ubertoken_fetcher.cc
+++ b/google_apis/gaia/ubertoken_fetcher.cc
@@ -7,6 +7,7 @@
 #include <vector>
 
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/rand_util.h"
 #include "base/time/time.h"
 #include "google_apis/gaia/gaia_auth_fetcher.h"
@@ -58,6 +59,8 @@ void UbertokenFetcher::OnUberAuthTokenFailure(
       // Calculate an exponential backoff with randomness of less than 1 sec.
       double backoff = base::RandDouble() + (1 << retry_number_);
       ++retry_number_;
+      UMA_HISTOGRAM_ENUMERATION("Signin.UberTokenRetry",
+          error.state(), GoogleServiceAuthError::NUM_STATES);
       retry_timer_.Stop();
       retry_timer_.Start(FROM_HERE,
                          base::TimeDelta::FromSecondsD(backoff),
@@ -79,6 +82,8 @@ void UbertokenFetcher::OnUberAuthTokenFailure(
     }
   }
 
+  UMA_HISTOGRAM_ENUMERATION("Signin.UberTokenFailure",
+      error.state(), GoogleServiceAuthError::NUM_STATES);
   consumer_->OnUbertokenFailure(error);
 }