Add serialization to PairingRegistry.

remoting/protocol/protocol_mock_objects.h

Index: remoting/protocol/protocol_mock_objects.h
diff --git a/remoting/protocol/protocol_mock_objects.h b/remoting/protocol/protocol_mock_objects.h
index 84960fdc8ad055802fd99372d243e7cabb7eb331..cfb912b71f873843c9011e9bd6fb6b9f611f2a69 100644
--- a/remoting/protocol/protocol_mock_objects.h
+++ b/remoting/protocol/protocol_mock_objects.h
@@ -222,11 +222,33 @@ class MockPairingRegistryDelegate : public PairingRegistry::Delegate {
   virtual void Load(
       const PairingRegistry::LoadCallback& callback) OVERRIDE;
 
+  // By default, the Save method runs its callback automatically because the
+  // negotiating authenticator unit test does not provide any hooks to do it
+  // manually. For unit tests that need to verify correct behaviour under
+  // asynchronous conditions, use this method to disable this feature and call
+  // RunCallback as appropriate.
+  void set_run_save_callback_automatically(
+      bool run_save_callback_automatically) {
+    run_save_callback_automatically_ = run_save_callback_automatically;
+  }
+
+  bool HasCallback() const {
+    return !load_callback_.is_null() || !save_callback_.is_null();
+  }
+
+  // Run either the save or the load callback (whichever was set most recently;
+  // it is an error for both of these to be set at the same time).
   void RunCallback();
 
  private:
+  void SetPairingsJsonAndRunCallback(
+      const std::string& pairings_json,
+      const PairingRegistry::SaveCallback& callback);
+
   base::Closure load_callback_;
+  base::Closure save_callback_;
   std::string pairings_json_;
+  bool run_save_callback_automatically_;
 };
 
 }  // namespace protocol