Implemented the GetSources() in native code.

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 b62c266ff696177aceadac0c64b34f071f2345a2..f74edfa9406ac81d13fc8a864a37c10a2ea9c7e1 100644
--- a/webrtc/test/mock_voe_channel_proxy.h
+++ b/webrtc/test/mock_voe_channel_proxy.h
@@ -13,9 +13,9 @@
 
 #include <string>
 
+#include "webrtc/modules/rtp_rtcp/source/rtp_packet_received.h"
 #include "webrtc/test/gmock.h"
 #include "webrtc/voice_engine/channel_proxy.h"
-#include "webrtc/modules/rtp_rtcp/source/rtp_packet_received.h"
 
 namespace webrtc {
 namespace test {
@@ -91,6 +91,7 @@ class MockVoEChannelProxy : public voe::ChannelProxy {
   MOCK_METHOD1(OnTwccBasedUplinkPacketLossRate, void(float packet_loss_rate));
   MOCK_METHOD1(OnRecoverableUplinkPacketLossRate,
                void(float recoverable_packet_loss_rate));
+  MOCK_CONST_METHOD0(GetSources, std::vector<RtpSource>());
 };
 }  // namespace test
 }  // namespace webrtc