Add tests for r8811.

All these tests crashed before r8811. These tests should've been with
that change but r8811 was pushed in before to make bots green.

BUG=1788, 1667
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/48669004

Cr-Commit-Position: refs/heads/master@{#8881}
diff --git a/talk/media/webrtc/webrtcvideoengine2_unittest.cc b/talk/media/webrtc/webrtcvideoengine2_unittest.cc
index 1cf015e..3f3966b 100644
--- a/talk/media/webrtc/webrtcvideoengine2_unittest.cc
+++ b/talk/media/webrtc/webrtcvideoengine2_unittest.cc
@@ -589,6 +589,19 @@
   EXPECT_EQ(0u, encoder_factory.encoders().size());
 }
 
+TEST_F(WebRtcVideoEngine2Test, CanConstructDecoderForVp9EncoderFactory) {
+  cricket::FakeWebRtcVideoEncoderFactory encoder_factory;
+  encoder_factory.AddSupportedVideoCodecType(webrtc::kVideoCodecVP9, "VP9");
+  std::vector<cricket::VideoCodec> codecs;
+  codecs.push_back(kVp9Codec);
+
+  rtc::scoped_ptr<VideoMediaChannel> channel(
+      SetUpForExternalEncoderFactory(&encoder_factory, codecs));
+
+  EXPECT_TRUE(
+      channel->AddRecvStream(cricket::StreamParams::CreateLegacy(kSsrc)));
+}
+
 VideoMediaChannel* WebRtcVideoEngine2Test::SetUpForExternalEncoderFactory(
     cricket::WebRtcVideoEncoderFactory* encoder_factory,
     const std::vector<VideoCodec>& codecs) {