Add AudioReceiveStream::SetGain() method and use that in WVoMC::SetOutputVolume().

webrtc/test/mock_voe_channel_proxy.h

Index: webrtc/test/mock_voe_channel_proxy.h
diff --git a/webrtc/test/mock_voe_channel_proxy.h b/webrtc/test/mock_voe_channel_proxy.h
index cc2c32b3736931bb02e34ea0771a3da4949a2c43..331ff2a47e202ffcd4d3a961113c6c725aa1f7ef 100644
--- a/webrtc/test/mock_voe_channel_proxy.h
+++ b/webrtc/test/mock_voe_channel_proxy.h
@@ -44,6 +44,8 @@ class MockVoEChannelProxy : public voe::ChannelProxy {
   MOCK_CONST_METHOD0(GetDelayEstimate, uint32_t());
   MOCK_METHOD1(SetSendTelephoneEventPayloadType, bool(int payload_type));
   MOCK_METHOD2(SendTelephoneEventOutband, bool(int event, int duration_ms));
+  // TODO(solenberg): Talk the compiler into accepting this mock method:
+  // MOCK_METHOD1(SetSink, void(std::unique_ptr<AudioSinkInterface> sink));

[kwiberg-webrtc, 2016/06/16 09:26:53]

You need icky workarounds for methods that return move-only values, but I'm not
aware of any particular problems with move-only arguments. What errors do you
get?

[the sun, 2016/06/16 14:34:06]

../../webrtc/test/mock_voe_channel_proxy.h:49:3: error: call to
implicitly-deleted copy constructor of
'std::__1::unique_ptr<webrtc::AudioSinkInterface,
std::__1::default_delete<webrtc::AudioSinkInterface> >'
  MOCK_METHOD1(SetSink, void(std::unique_ptr<AudioSinkInterface> sink));

(Since the change is orthogonal to this CL, I'll just leave it commented out for
now. I merely went through the methods and noticed this one missing.)

   MOCK_METHOD1(RegisterExternalTransport, void(Transport* transport));
   MOCK_METHOD0(DeRegisterExternalTransport, void());
   MOCK_METHOD3(ReceivedRTPPacket, bool(const uint8_t* packet,
@@ -52,6 +54,7 @@ class MockVoEChannelProxy : public voe::ChannelProxy {
   MOCK_METHOD2(ReceivedRTCPPacket, bool(const uint8_t* packet, size_t length));
   MOCK_CONST_METHOD0(GetAudioDecoderFactory,
                      const rtc::scoped_refptr<AudioDecoderFactory>&());
+  MOCK_METHOD1(SetChannelOutputVolumeScaling, void(float scaling));
 };
 }  // namespace test
 }  // namespace webrtc