shill: Add function to pretty-print result from ConnectionHealthChecker.

BUG=chromium:229982
TEST=build and run unit-tests.

Change-Id: I19d0b29bca278d28d7521871e03f0c1097f821d6
Reviewed-on: https://gerrit.chromium.org/gerrit/47789
Reviewed-by: Arman Uguray <armansito@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Commit-Queue: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/connection_health_checker.h b/connection_health_checker.h
index f788878..22ace95 100644
--- a/connection_health_checker.h
+++ b/connection_health_checker.h
@@ -39,6 +39,7 @@
  public:
   typedef std::queue<IPAddress> IPAddressQueue;
 
+  // TODO(pprabhu): Rename kResultElongatedTimeWait to kResultTearDownFailure.
   enum Result {
     // There was some problem in the setup of ConnctionHealthChecker.
     // Could not attempt a tcp connection.
@@ -84,6 +85,8 @@
   // Calling Stop() on a Stop()ed health check is a no-op.
   virtual void Stop();
 
+  static const char *ResultToString(Result result);
+
   // Accessors.
   const IPAddressQueue &remote_ips() { return remote_ips_; }
   void set_run_data_test(bool val) { run_data_test_ = val; }