Revert "Revert "Fix #839 #838""

This reverts commit 264b177b38.

src/main/scala/com/github/shadowsocks/ShadowsocksApplication.scala

@@ -46,7 +46,7 @@ import android.app.Application
 import android.preference.PreferenceManager
 import android.support.v7.app.AppCompatDelegate
 import com.github.shadowsocks.database.{DBHelper, ProfileManager}
-import com.github.shadowsocks.utils.{Key, Utils}
+import com.github.shadowsocks.utils.{Key, Utils, TcpFastOpen}
 import com.google.android.gms.analytics.{GoogleAnalytics, HitBuilders, StandardExceptionParser}
 import com.google.android.gms.common.api.ResultCallback
 import com.google.android.gms.tagmanager.{ContainerHolder, TagManager}
@@ -111,6 +111,13 @@ class ShadowsocksApplication extends Application {
       }
     }
     pending.setResultCallback(callback, 2, TimeUnit.SECONDS)
+
+    // TFO
+    val tfo = settings.getBoolean(Key.tfo, false)
+    if (tfo && !TcpFastOpen.isEnabled)
+    {
+      TcpFastOpen.enabled(true)
+    }
   }
 
   def refreshContainerHolder {