Remove VoEExternalMedia interface.

webrtc/voice_engine/BUILD.gn

Index: webrtc/voice_engine/BUILD.gn
diff --git a/webrtc/voice_engine/BUILD.gn b/webrtc/voice_engine/BUILD.gn
index 22739af4a1ecf6e313e60973bfbe1cc31703ca9a..028e4d198564f763a23394dfc84360b4efc17e58 100644
--- a/webrtc/voice_engine/BUILD.gn
+++ b/webrtc/voice_engine/BUILD.gn
@@ -78,7 +78,6 @@ rtc_static_library("voice_engine") {
     "include/voe_base.h",
     "include/voe_codec.h",
     "include/voe_errors.h",
-    "include/voe_external_media.h",
     "include/voe_file.h",
     "include/voe_hardware.h",
     "include/voe_neteq_stats.h",
@@ -106,8 +105,6 @@ rtc_static_library("voice_engine") {
     "voe_base_impl.h",
     "voe_codec_impl.cc",
     "voe_codec_impl.h",
-    "voe_external_media_impl.cc",
-    "voe_external_media_impl.h",
     "voe_file_impl.cc",
     "voe_file_impl.h",
     "voe_hardware_impl.cc",
@@ -277,7 +274,6 @@ if (rtc_include_tests) {
       "test/channel_transport/udp_socket_manager_unittest.cc",
       "test/channel_transport/udp_socket_wrapper_unittest.cc",
       "test/channel_transport/udp_transport_unittest.cc",
-      "transmit_mixer_unittest.cc",
       "transport_feedback_packet_loss_tracker_unittest.cc",
       "utility_unittest.cc",
       "voe_audio_processing_unittest.cc",
@@ -371,7 +367,6 @@ if (rtc_include_tests) {
         "test/auto_test/standard/codec_before_streaming_test.cc",
         "test/auto_test/standard/codec_test.cc",
         "test/auto_test/standard/dtmf_test.cc",
-        "test/auto_test/standard/external_media_test.cc",
         "test/auto_test/standard/file_before_streaming_test.cc",
         "test/auto_test/standard/file_test.cc",
         "test/auto_test/standard/hardware_before_initializing_test.cc",