[Remoting Android] Move pairing secret fetcher to the network thread

remoting/client/jni/jni_pairing_secret_fetcher.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef REMOTING_CLIENT_JNI_JNI_PAIRING_SECRET_FETCHER_H_
 #define REMOTING_CLIENT_JNI_JNI_PAIRING_SECRET_FETCHER_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "remoting/protocol/client_authentication_config.h"
 
 namespace remoting {
 
 class ChromotingJniRuntime;
 class JniClient;
 
-// This class fetches the pairing secret on the UI thread. It must be deleted
-// on UI.
+// This class fetches the pairing secret on the UI thread. It is used entirely
+// on the network thread.

[Lambros, 2016/06/07 01:21:12]

Actually, it's created on the UI thread, but thereafter used on the network
thread.

[Yuwei, 2016/06/07 18:01:03]

Done. Fixed comments.

 class JniPairingSecretFetcher {
  public:
   JniPairingSecretFetcher(ChromotingJniRuntime* runtime,
                    base::WeakPtr<JniClient> client,
                    const std::string& host_id);
   virtual ~JniPairingSecretFetcher();
 
-  // Called on UI thread. Notifies the user interface that the user needs to
-  // enter a PIN. The current authentication attempt is put on hold until
-  // |callback| is invoked. |callback| will be run on the network thread.
+  // Notifies the user interface that the user needs to enter a PIN. The current
+  // authentication attempt is put on hold until |callback| is invoked.
   void FetchSecret(bool pairable,
                    const protocol::SecretFetchedCallback& callback);
 
   // Provides the user's PIN and resumes the host authentication attempt. Call
-  // on the UI thread once the user has finished entering this PIN into the UI,
-  // but only after the UI has been asked to provide a PIN (via FetchSecret()).
+  // once the user has finished entering this PIN into the UI, but only after
+  // the UI has been asked to provide a PIN (via FetchSecret()).
   void ProvideSecret(const std::string& pin);
 
   // Get weak pointer to be used on the UI thread.
   base::WeakPtr<JniPairingSecretFetcher> GetWeakPtr();

[Lambros, 2016/06/07 01:21:12]

Can this be removed?

[Yuwei, 2016/06/07 17:36:00]

Currently JniClient passes in a WeakPtr of the secret fetcher to the
JniInstance. We can make that pointer a raw pointer since secret_fetcher_ will
always be deleted after JniInstance is deleted. I personally prefer WeakPtr
since we don't need to care too much about the deletion order... WDYT?

[Yuwei, 2016/06/07 17:44:26]

Hmm... Just thought about this again... The ctor of JniInstance is doing
something like:

client_auth_config_.fetch_secret_callback =
base::Bind(&JniPairingSecretFetcher::FetchSecret, secret_fetcher);

Looks like secret_fetcher.FetchSecret() will be run on the network thread at
some point... I think it's safer to use WeakPtr in this case...

 
  private:
+  static void FetchSecretOnUI(base::WeakPtr<JniClient> client,

[Lambros, 2016/06/07 01:21:12]

rename: FetchSecretOnUiThread

[Yuwei, 2016/06/07 18:01:03]

Done.

+                              const std::string& host_id,
+                              bool pairable);
+
   ChromotingJniRuntime* jni_runtime_;
   base::WeakPtr<JniClient> jni_client_;
 
   std::string host_id_;
 
   // Pass this the user's PIN once we have it. To be assigned and accessed on
   // the UI thread, but must be posted to the network thread to call it.
   protocol::SecretFetchedCallback callback_;
 
   base::WeakPtrFactory<JniPairingSecretFetcher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(JniPairingSecretFetcher);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_JNI_JNI_PAIRING_SECRET_FETCHER_H_