Fix RTX-configuration test with >2 codecs built.

webrtc/media/engine/webrtcvideoengine2_unittest.cc

Index: webrtc/media/engine/webrtcvideoengine2_unittest.cc
diff --git a/webrtc/media/engine/webrtcvideoengine2_unittest.cc b/webrtc/media/engine/webrtcvideoengine2_unittest.cc
index 0a04fc78caf2e2afe4ca7e5eacad9757456bad7d..7c7fa27700501a10463d91c3241df0f44d1f2342 100644
--- a/webrtc/media/engine/webrtcvideoengine2_unittest.cc
+++ b/webrtc/media/engine/webrtcvideoengine2_unittest.cc
@@ -3207,9 +3207,13 @@ TEST_F(WebRtcVideoChannel2Test, DefaultReceiveStreamReconfiguresToUseRtx) {
   ASSERT_EQ(1u, fake_call_->GetVideoReceiveStreams().size())
       << "AddRecvStream should've reconfigured, not added a new receiver.";
   recv_stream = fake_call_->GetVideoReceiveStreams()[0];
-  ASSERT_GE(2u, recv_stream->GetConfig().rtp.rtx.size());
-  EXPECT_EQ(rtx_ssrcs[0],
-            recv_stream->GetConfig().rtp.rtx.begin()->second.ssrc);
+  EXPECT_FALSE(recv_stream->GetConfig().rtp.rtx.empty());
+  EXPECT_EQ(recv_stream->GetConfig().decoders.size(),
+            recv_stream->GetConfig().rtp.rtx.size())
+      << "RTX should be mapped for all decoders/payload types.";
+  for (const auto& kv : recv_stream->GetConfig().rtp.rtx) {
+    EXPECT_EQ(rtx_ssrcs[0], kv.second.ssrc);
+  }
 }
 
 TEST_F(WebRtcVideoChannel2Test, RejectsAddingStreamsWithMissingSsrcsForRtx) {