Implemented the GetSources() in native code.

webrtc/modules/rtp_rtcp/BUILD.gn

 # Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../../webrtc.gni")
 
@@ skipping 149 matching lines @@
     defines = [ "BWE_TEST_LOGGING_COMPILE_TIME_ENABLE=0" ]
   }
 
   if (!build_with_chromium && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     "../..:webrtc_common",
+    "../../api:libjingle_peerconnection_api",
     "../../api:transport_api",
     "../../api/audio_codecs:audio_codecs_api",
     "../../base:gtest_prod",
     "../../base:rtc_base_approved",
     "../../base:rtc_task_queue",
     "../../call:call_interfaces",
     "../../common_video",
     "../../logging:rtc_event_log_api",
     "../../system_wrappers",
     "../audio_coding:audio_format_conversion",
@@ skipping 87 matching lines @@
       "source/rtp_fec_unittest.cc",
       "source/rtp_format_h264_unittest.cc",
       "source/rtp_format_vp8_test_helper.cc",
       "source/rtp_format_vp8_test_helper.h",
       "source/rtp_format_vp8_unittest.cc",
       "source/rtp_format_vp9_unittest.cc",
       "source/rtp_header_extension_unittest.cc",
       "source/rtp_packet_history_unittest.cc",
       "source/rtp_packet_unittest.cc",
       "source/rtp_payload_registry_unittest.cc",
+      "source/rtp_receiver_unittest.cc",
       "source/rtp_rtcp_impl_unittest.cc",
       "source/rtp_sender_unittest.cc",
       "source/rtp_utility_unittest.cc",
       "source/time_util_unittest.cc",
       "source/ulpfec_generator_unittest.cc",
       "source/ulpfec_header_reader_writer_unittest.cc",
       "source/ulpfec_receiver_unittest.cc",
       "source/vp8_partition_aggregator_unittest.cc",
       "test/testAPI/test_api.cc",
       "test/testAPI/test_api.h",
@@ skipping 16 matching lines @@
     ]
 
     # TODO(jschuh): bugs.webrtc.org/1348: fix this warning.
     configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
     if (!build_with_chromium && is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
   }
 }