Prevent the frame decryptor being set if the channel is stopped.

This change deals with a race condition if the media channel has been stopped
and is in the process of changing while we get a call to set a FrameDecryptor
or FrameEncryptor.

Bug: webrtc:9926, webrtc:9932
Change-Id: Ie2da2fa1f31f5cb5eb0b481861a7008e635f562d
Reviewed-on: https://webrtc-review.googlesource.com/c/107986
Commit-Queue: Benjamin Wright <benwright@webrtc.org>
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Reviewed-by: Seth Hampson <shampson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25398}

pc/rtpsenderreceiver_unittest.cc

diff --git a/pc/rtpsenderreceiver_unittest.cc b/pc/rtpsenderreceiver_unittest.cc
index 70b1601..fa42615 100644
--- a/pc/rtpsenderreceiver_unittest.cc
+++ b/pc/rtpsenderreceiver_unittest.cc
@@ -1424,6 +1424,18 @@
             audio_rtp_sender_->GetFrameEncryptor().get());
 }
 
+// Validate that setting a FrameEncryptor after the send stream is stopped does
+// nothing.
+TEST_F(RtpSenderReceiverTest, AudioSenderCannotSetFrameEncryptorAfterStop) {
+  CreateAudioRtpSender();
+  rtc::scoped_refptr<FrameEncryptorInterface> fake_frame_encryptor(
+      new FakeFrameEncryptor());
+  EXPECT_EQ(nullptr, audio_rtp_sender_->GetFrameEncryptor());
+  audio_rtp_sender_->Stop();
+  audio_rtp_sender_->SetFrameEncryptor(fake_frame_encryptor);
+  // TODO(webrtc:9926) - Validate media channel not set once fakes updated.
+}
+
 // Validate that the default FrameEncryptor setting is nullptr.
 TEST_F(RtpSenderReceiverTest, AudioReceiverCanSetFrameDecryptor) {
   CreateAudioRtpReceiver();
@@ -1435,4 +1447,60 @@
             audio_rtp_receiver_->GetFrameDecryptor().get());
 }
 
+// Validate that the default FrameEncryptor setting is nullptr.
+TEST_F(RtpSenderReceiverTest, AudioReceiverCannotSetFrameDecryptorAfterStop) {
+  CreateAudioRtpReceiver();
+  rtc::scoped_refptr<FrameDecryptorInterface> fake_frame_decryptor(
+      new FakeFrameDecryptor());
+  EXPECT_EQ(nullptr, audio_rtp_receiver_->GetFrameDecryptor());
+  audio_rtp_receiver_->Stop();
+  audio_rtp_receiver_->SetFrameDecryptor(fake_frame_decryptor);
+  // TODO(webrtc:9926) - Validate media channel not set once fakes updated.
+}
+
+// Validate that the default FrameEncryptor setting is nullptr.
+TEST_F(RtpSenderReceiverTest, VideoSenderCanSetFrameEncryptor) {
+  CreateVideoRtpSender();
+  rtc::scoped_refptr<FrameEncryptorInterface> fake_frame_encryptor(
+      new FakeFrameEncryptor());
+  EXPECT_EQ(nullptr, video_rtp_sender_->GetFrameEncryptor());
+  video_rtp_sender_->SetFrameEncryptor(fake_frame_encryptor);
+  EXPECT_EQ(fake_frame_encryptor.get(),
+            video_rtp_sender_->GetFrameEncryptor().get());
+}
+
+// Validate that setting a FrameEncryptor after the send stream is stopped does
+// nothing.
+TEST_F(RtpSenderReceiverTest, VideoSenderCannotSetFrameEncryptorAfterStop) {
+  CreateVideoRtpSender();
+  rtc::scoped_refptr<FrameEncryptorInterface> fake_frame_encryptor(
+      new FakeFrameEncryptor());
+  EXPECT_EQ(nullptr, video_rtp_sender_->GetFrameEncryptor());
+  video_rtp_sender_->Stop();
+  video_rtp_sender_->SetFrameEncryptor(fake_frame_encryptor);
+  // TODO(webrtc:9926) - Validate media channel not set once fakes updated.
+}
+
+// Validate that the default FrameEncryptor setting is nullptr.
+TEST_F(RtpSenderReceiverTest, VideoReceiverCanSetFrameDecryptor) {
+  CreateVideoRtpReceiver();
+  rtc::scoped_refptr<FrameDecryptorInterface> fake_frame_decryptor(
+      new FakeFrameDecryptor());
+  EXPECT_EQ(nullptr, video_rtp_receiver_->GetFrameDecryptor());
+  video_rtp_receiver_->SetFrameDecryptor(fake_frame_decryptor);
+  EXPECT_EQ(fake_frame_decryptor.get(),
+            video_rtp_receiver_->GetFrameDecryptor().get());
+}
+
+// Validate that the default FrameEncryptor setting is nullptr.
+TEST_F(RtpSenderReceiverTest, VideoReceiverCannotSetFrameDecryptorAfterStop) {
+  CreateVideoRtpReceiver();
+  rtc::scoped_refptr<FrameDecryptorInterface> fake_frame_decryptor(
+      new FakeFrameDecryptor());
+  EXPECT_EQ(nullptr, video_rtp_receiver_->GetFrameDecryptor());
+  video_rtp_receiver_->Stop();
+  video_rtp_receiver_->SetFrameDecryptor(fake_frame_decryptor);
+  // TODO(webrtc:9926) - Validate media channel not set once fakes updated.
+}
+
 }  // namespace webrtc