[GCM] Add port 443 fallback logic and histograms

google_apis/gcm/engine/connection_factory_impl.h

Index: google_apis/gcm/engine/connection_factory_impl.h
diff --git a/google_apis/gcm/engine/connection_factory_impl.h b/google_apis/gcm/engine/connection_factory_impl.h
index 967c6c1ae46d0fc820ca02e51a82f4f8b4a297bb..591264efb48691413a5cee2d734bd28958e8a2b3 100644
--- a/google_apis/gcm/engine/connection_factory_impl.h
+++ b/google_apis/gcm/engine/connection_factory_impl.h
@@ -32,7 +32,7 @@ class GCM_EXPORT ConnectionFactoryImpl :
     public net::NetworkChangeNotifier::IPAddressObserver {
  public:
   ConnectionFactoryImpl(
-      const GURL& mcs_endpoint,
+      const std::vector<GURL>& mcs_endpoints,
       const net::BackoffEntry::Policy& backoff_policy,
       scoped_refptr<net::HttpNetworkSession> network_session,
       net::NetLog* net_log);
@@ -54,6 +54,11 @@ class GCM_EXPORT ConnectionFactoryImpl :
       net::NetworkChangeNotifier::ConnectionType type) OVERRIDE;
   virtual void OnIPAddressChanged() OVERRIDE;
 
+  // Returns the server to which the factory is currently connected, or if
+  // no connection is active the server to which the next connection attempt
+  // will be made.
+  GURL GetCurrentEndpoint() const;
+
  protected:
   // Implementation of Connect(..). If not in backoff, uses |login_request_|
   // in attempting a connection/handshake. On connection/handshake failure, goes
@@ -89,8 +94,12 @@ class GCM_EXPORT ConnectionFactoryImpl :
 
   void CloseSocket();
 
-  // The MCS endpoint to make connections to.
-  const GURL mcs_endpoint_;
+  // The MCS endpoints to make connections to, sorted in order of priority.
+  const std::vector<GURL> mcs_endpoints_;
+  // Index to the endpoint for which a connection should be attempted next.
+  size_t next_endpoint_;
+  // Index to the endpoint that was last successfully connected.
+  size_t last_successful_endpoint_;
 
   // The backoff policy to use.
   const net::BackoffEntry::Policy backoff_policy_;